It’s probably only a matter of time before popular forums lock down even view access to everything except Google, forcing people to use and work with monopolies and shutting out smaller player permanently

The reason they can get away with it is because too many people use Chrome / Edge / Brave (Chromium based browsers). The free web will survive if companies lose half their customers by not supporting it. It won't survive if they would only lose 0.1% of their customers.

So the key will be to push non-Chromium browsers - get that installed base up. Encourage everyone you know to use a non-Chromium browser. Install a decent browser for your elderly relatives, and spread the word.

Sounds like it's a good time to set up a Jellyfin server with your music and movies, and a Kavita server with comics and books! Yo ho ho!... I wonder how many of my friends I can get back onto IRC? :D

If this shit is left unchecked, mainstream websites will stop working with open web browsers like Firefox.

It's not like we're far away from that now. While most sites work with Firefox, I still have to use Edge on a regular basis because some sites just don't work on Firefox, and somehow we've reached a point where Edge is the lesser evil because the other choice is Chrome. And I recently discovered a website that won't work on Firefox or Edge, and as it wasn't a website that I had a choice about using (needed to use it to respond to a letter from a government body), there was no choice but to install Chrome.

There's power in organizing and voting with your wallet collectively. Reject companies that trample your customer needs and convince others to do the same.