The fundamental problem is that a web engine is one of the most massively complex pieces of software that we currently use. There are a ridiculous number of standards and behaviors that a modern web browser needs to implement, as well as a whole host of security implications that need constant updating. It's not like the majority of other software projects, where a determined solo dev or even small group can strike out on their own. It really requires a team of dozens or hundreds of developers putting in consistent effort, which basically means a corporate entity.

surely if Web Devs tell them to go pound sand, or intentionally break the site when using Google Chrome, and put a message saying, “Go to Firefox / Safari for a better experience”, that will make Google backtrack.

Riiight... User will surely do that instead of simply never visiting your site again.

What is stopping someone; say the FSF or some other group championing libre software from coming up with their own web engine completely different from the incumbent engines?

Seems you're not aware of stuff like Servo, which some said was supposed to be the replacement of Gecko, and it's being written in Rust. But Mozilla ditched it and gave it to the Linux Foundation where its development is reeeaaally sloooooooow.

Afaik The Linux Foundation gives next-to-nothing, if not nothing, to its development. But despite of all of that it seems it has increased its pace (compared to the time it was just given to TLF) and has got donations and stuff.

But a browser engine is an absurdly huge piece of software and it will be a miracle if projects like Rust (or Ladybird, which I just learned it's targeting its first alpha for... 2026!) get backed by big corporations and their pace gets quicker.

Call me stupid or whatever (seeing the Reddit toxicity that has got into Lemmy I'd be surprised if this has no downvotes!) but I do think Servo has the potential to be a serious contender to the hegemony of Chrome/Chromium in the long haul. The Linux Foundation seems to have enough resources to propel its development and reach that goal, but they just choose not to nor seem to care at all. So yes, unless a miracle happens we normies can only choose between Chrome/Chromium, Firefox or something Webkit. Maybe even going absolutely radical and using Konqueror with its KHTML engine, if you can.

Modern web engines are basically mini operating systems. Long gone are the days where a web browser just needed to render basic HTML pages, handle some simple protocol actions, and render images.

To build something that supports all of the latest web standards, is secure, is always up to date, and on top of all that, is performant, requires a large group of very skilled devs working constantly on all those components.

Web development, for better or worse, has become a massive and rapidly evolving ecosystem that is constantly morphing and changing. Web apps are becoming the standard, and even "simple" modern websites are absolutely filled with different widgets and frameworks for all the different elements they contain.

If a very large/rich org or company decided to dedicate a whole team of devs to build a FOSS web engine, it could happen, but that used to be Mozilla, and look how that has slowly been failing.

What person with a website that has any significant traffic would willingly break it for 80+ percent of its users? That will never happen, sadly.

but surely we need more diversity than just the existing three to spur more development, right?

Ideally, of course. In practice, to me, it looks like it's a very hard thing to do.

Don't let that discourage you from taking on the endeavour though! I too would like another option!

What is stopping someone; say the FSF or some other group championing libre software from coming up with their own web engine completely different from the incumbent engines?

Building a browser engine is hard, especially when the target is moving at a rapid pace, and that target is controlled by Google. Like it or not, the web as it is today, is pretty much driven by Google (and to a lesser extent by Apple and Microsoft) these days. They can throw infinite resources into developing the browser engine and the browser itself. The closest competitor we have today is likely Servo, and they scrape by on pennies.

Developing something from scratch, with even less funding and expertise than Servo is a non-starter. It's not going to happen. Sure, sure, there's LadyBird and some other independent efforts, but I very highly doubt they'll ever catch up to the three major engines.

To develop and maintain a browser, you need people, and they need to be paid. Paying open source developers is... quite a big problem in and of itself, even for things considerably easier and smaller in scale than a web browser.

surely if Web Devs tell them to go pound sand, or intentionally break the site when using Google Chrome, and put a message saying, “Go to Firefox / Safari for a better experience”, that will make Google backtrack.

They would not, because for every developer who would do this, there's 100 who would not, because their livelihood depends on people with Google browsers being able to use their stuff. Google is in a position of power here: they are the #1 search engine, they are the #1 browser, they're pretty well positioned on the mobile phone market too. The vast majority of businesses (companies or individuals, doesn't matter) simply can't afford to go against Google.

If the vast majority would, then yeah, Google would backtrack. But that would require a coordinated effort, from the vast majority of the internet. Likely multiple months of protest. That's not going to happen, people can't afford it.

most defunct / unmaintained and the three: blink, gecko and webkit being the only ones actively developed and maintained today (I am aware of Goanna, but some articles online say it isn’t being developed anymore – I could be wrong).

The fourth most developed browser engine is Ladybird, spun off from the SerenityOS project. It's very active. And then you have Mozilla's Servo... kinda. And then Goanna is still maintained, but not too active.

Building a full function browser is a huge project that can really only be done by a big organization. And it's mostly for the benefit of advertisers and other hucksters, so not a satisfying thing to work on for purely charitable reasons. Basically the web sucks. We'd be better off with a privacy protecting fragment that was designed for end users rather than for upstream. See Rfc 8890 for more.

Well, there is this one: https://ladybird.org/

FOSS community is just highly triggerable and sore. Try to say anything they disagree with to check it.