Having had much success over the years with the results I had been able to achieve implementing SEO white-hat strategies on a multi-page website (personally designed/developed using CoffeeCup HTML Editor back in 2011) without ever having to rely on paid ads, I must admit I had a number of reservations in electing to go with a single-page website for launching a new business. While I didn't expect to see results overnight, given what I had been able to accomplish over a short period of time providing SEO for multi-page websites in the past, I am extremely disappointed in my SEO progress thus far regarding my single-page site as it appears to be nowhere found on the web other than when typing the URL into my browser's address bar. All considered, has anyone had much success in providing SEO for a single-page website without having to rely on paid ads? Also, has anyone provided SEO for both single and multi-page websites over a long enough period of time to render an opinion as to which one has proven to be most effective for their SEO efforts? Thank you ahead of time.

Hi
This may or may not answer your question, you may or may not already be aware and knowledgeable about the following suggestion.

This is a simplified version of a complicated subject
On March 5th, 2020 Google announced new plans to change the way that the indexer thing displays websites on its SERP's

Simply put it was now going to place all search results from their customer's search queries based on
MOBILE-FIRST which basically meant how user-friendly the site is for their customers, and if a site DIDN't meet that requirement it would not even appear on desktop searches not only that but they also announced that they would no longer be putting multi-pages from a site, it would be limited to 1 page or perhaps a maximum of 2 pages per site if the indexing thingy couldn't make it's artificially intelligent mind up between page relevance/

March 2021
Google finally announced that the changes to the Index thingy that announced in 2020 were going to be implemented forthwith (although it actually was April really)

So what does that mean for your site?
First of all, I am mentioning Google as they are still the big boys in the browser game, others will and have followed along some may never,

KEYWORDS
It is a known statistic (rather than fact) that most users on mobile devices, search using VOICE and that they sort of ask in a natural way rather than using just one or two keywords (as was the old fashioned wat)

So for the sake of other search engines & for google too, your keywords section in the header, needs to be populated (nothing in there at the moment, blank, empty space, a void, ) You need to be thinking about long-tail keywords, conversational questions that might be asked, etc.

For the sake of Google you need to be including such things in your content on the page, (and as close the top for the better ones as possible, although not written in stone they can be placed anywhere on the page a nice spread is ok/

Your site is pretty much ok for mobile-friendliness, just a couple of minor things, but not really ones that should cause too much of an issue.

One thing that you do not have is a site privacy policy, In many places, this is no longer an option, but is a legal requirement to do with Data Protection, whilst this shouldn't be an SEO thing, it might still be having some sort of effect (as in a competitor having one and you not having one, maybe that the ones with gets higher rankings than the one without.

At the same time, you should also have a Site Terms & Conditions policy, or a Site Use Policy if not only to just cover your bum in the event of someone doing something wrong or malicious.

The least you should do is the keywords thingy, and see how the waters flow after that

Update
Although your site doesn't use any cookies (which is in itself strange not even essential or temporary ones) It might be worth mentioning( if you decide to have one) in a privacy policy section about cookies, that you do not place cookies of any description on their browser/device. but if they follow any links to other sites that you have on your page, they may put cookies on the browser/device (third-party cookies) to which you have no control over, and that they are not obliged to tell you what cookies those sites may use or place on your visitor's browser/device.

Once again not really a direct impact on SEO but a nice thing to inform your visitors (which = potential clients) and something that the likes of Google will look at favorably.

UPDATE UPDATE

I should have mentioned that the Mobile-First/Friendliness thingy Google introduced is for New Sites (or old domains with new content/page names/descriptions etc) old & existing sites will still for the time being be listed on desktop search results, UNTIL they can get around to bringing all into the same way (who knows how long that will be what with the enormous amount of websites out there)

On a good note, your website IS CONSIDERED mobile-friendly by Google so therefore I would suggest that the major drawback is those search requests keywords and the positioning of such in your content be placed higher up the page.

Google has a tool that can look at your site with regard to issues, https://search.google.com/search-console/welcome?utm_source=about-page to use it you need to enter your sites URL, and then verify that you are the owner.
its pretty good at finding any issues that are holding back your ranking on SERPs, and as I said before fix any issues with Google and you will be good to go on other browsers

@WayanJaya
In answer to your replies, yes, I am and have only been too aware of Google's emphasis on mobile devices that actually started well b4 2020. This was essentially the primary reason I overhauled an 8-year old multi-page website (at the time) to a responsive website in November 2019. Based on everything I had read back then, I felt this to be long overdue and well worth doing given my former multi-page website was not a responsive website even though it appeared on the first page of the SERPs (without ever having to rely on paid ads) for a number of my website pages related to several primary keywords. Unfortunately, the Coronavirus devastated the commercial RE industry along with my former profession and everything I had accomplished with my site up to that point in time leaving me with a responsive multi-page website with a first page organic ranking in the SERPs in positions 1-5 for several pages generating little to no traffic attributed to the pandemic. While I didn't achieve a first-page ranking overnight without having to rely on paid ads, given my experience to date with a single-page site, I tend to agree with the majority of articles I have read to date that there exist too many SEO limitations when it comes to ranking for more than one keyword. In reality, I believe it's very difficult for a single-page website to rank for more than one primary keyword whether short or long-tail. And while quality content appears to be Google's number one priority, I don't believe great content alone can compensate for the keyword limitation posed by a single-page website. All considered I should have inquired in my initial post if anyone on the forum well versed in SEO has been able to achieve as much success with a single-page site as they have had with a multi-page site when it comes to ranking in the SERPs without having to rely on paid ads. Based on my experience to date, I would have to agree with almost everything I have read that the majority of single-page sites do not perform as well as multi-page sites when it comes to implementing proven white-hat SEO strategies. I should also state that if you were referring to the single-page site at https://www.seoauditspecialists.com referred to in one of my previous posts, this isn't the website. The URL really isn't important since it happens to be a responsive website that already scores high in being deemed mobile-friendly, so that's not an issue. It also scores well in GT Metrix, Google PageSpeed, and other online website audit tools with a proven track record. This noted, once again I'm inclined to believe that single-page sites simply cannot compete with responsive multi-page websites when it comes to SEO. And while I realize the importance of having a responsive website (regardless of the number of pages) to satisfy the majority who happen to be married to their mobile phones, many responsive websites are still better viewed on a desktop/laptop device which many in business will attest to. Hopes this serves to clarify the answer I'm looking for.

Sorry, I should have also added in my previous reply that I am altogether familiar with both Google's search console and Google Analytics which I've used for years. Once again, I am primarily interested in knowing if anyone on the forum has been successful in achieving first-page organic ranking in the SERPs for a single-page website using acceptable SEO white-hat strategies without having to rely on paid ads. Thank you ahead of time.

Please excuse my butting in here with something off-topic.

But Boilermaker, if you want people to actually take the trouble of reading what you write, you really should divide the contents of your posts into suitable portions, I'm talking about paragraphs. Reading on-screen can be tough enough, and this long 'chunk' above here really feels like an exercise in the impossible. I gave up after having read about half, losing the position at every second line break and having to start over again.

To answer your actual question
Yes I have many times achieved first page ranking with single page sites
Using the tools and methods I mentioned, in particular the keywords worked a treat in all cases and more than 1 on a page.

Normal length of time for inclusion on the SERPs 2 months or so, with some work (rather than spending time waffling) I have sometimes got it down to 7 days for results appearing.
A simple answer to what should have been a simple question.

All this talk about seo reminds me of this.

https://archive.google.com/pigeonrank/