This just happened overnight.
I see nothing on this site which requires this.
Why was there no notification?
What I had been using was Firefox which I haven’t upgraded because they changed the UI. I am temporarily posting with Microsoft Edge.
DuckDuckGo browser works great.
Totally different App from the search engine.
Fireproof the SDMB so you don’t have to constantly log in.
Pressing the Flame closes all Tabs and clears the cache. I have mine set to do this automatically when I close the browser.
Total privacy. No history, no cookies, nothing.
I also use Firefox, and I haven’t seen any change in the UI for a long time. It still works for me (though I’m on whatever is the current most recent Firefox version).
Moved to Site Feedback (from ATMB)
Discourse doesn’t send out notifications when they update their software. We don’t even know about it unless someone reports an issue or we specifically go looking to see if it changed.
I looked through the release notes, and this is listed under “Bug Fixes”. This is all they say about it.
That at least suggests you might work around this (for now) with an extension that can change your User Agent to pretend you’re using a later version of Firefox.
Though I would personally recommend updating Firefox or finding a spinoff that keeps the UI you like. If you update, you may be able to find tweaks to put the UI back.
It’s just not good to be using a browser that is that outdated as your main browser. Updates come with security improvements as well.
I used to use Pale Moon since that is basically Firefox before they screwed up Firefox, but Pale Moon does keep up with security patches, etc.
Unfortunately, Pale Moon doesn’t work with the SDMB either.
I use Waterfox Classic, which maintained the old Firefox UI I loved so much, but that’s now failing too often on modern sites, so I have slowly been building Waterfox Current to match as closely as possible the UI I prefer, and I guess this is the sign I need to finally make the full switchover.
I use Firefox. I’ve never gotten that message here, but when I do get it on other sites, I ignore it and keep on using FF. Usually it works fine.
I don’t like Edge. I have to use it for one thing, but I don’t like it.
Once I accepted the newer Chromium-based Edge (even Microsoft gave up on the older one which was trash, I could never stand it) my life has been so much better. Especially with a few plugins that make it more comfortable.
Everything works fine everywhere.
And I was a Firefox fan forever. Mozilla before it, and Netscape before that. I was a fan of its various iterations for decades. So I get the attachment.
Hopefully they’ll fix this bug. I’m sure they’re working on it, Discourse has been good about fixing these sorts of things.
(If they can just fix the way dates are displayed…)
I was a Google Chrome guy until a month or two ago. Switched to new (=Chromium) Edge and after relearning a couple keystrokes have been very happy. Current Edge is definitely less of a resource hog than current Chrome.
IMO FF became irritatingly obsolete about 6 years ago.
It’s not really a bug. OP is using a browser version that is at least a year out of date.
It’s literally in their list of bug fixes. Anything the developer calls a bug, is a bug. I agree with you that it should be perfectly valid to put the onus back on the person using the browser to update it or the system around it, but if the developer intends to support an older browser, then they will try to fix it, and it’s considered a bug.
Something being under “bug fixes” in release notes usually means “Here’s a bug we fixed”, not “here’s a bug we still need to fix”. So basically, the bug was “we weren’t telling you that older versions of Firefox weren’t supported, when we should have.”
I didn’t look at it that way. In that case, never mind. This is what happens when you don’t maintain your system properly. Your car will also stop running if you never change the oil. 
I followed BigT’s advice and added a User-Agent add-on and it works fine again. For those of you who think I have an outdated-system exactly what has changed in web standards (https, etc) in the last year or so? [I have Firefox 88; they made irritating changes in the UI with version 89]
Firefox is on version 102. There are going to be a lot of changes over 14 versions. Version 91 itself had over 18 sub-versions/revisions.
I do commend on a fine username/post combo, though.
Newer browsers get new information about certificates.
Securing communication over the internet is hard, impossible with obsolete browsers. Using a current browser is an essential part of computer hygiene.
Any version of any browser that is not the latest is obsolete.
It’s not that web standards have changed all that much. It’s that updates also mean security fixes. That sounds like nearly two years ago, which is an eternity in the software world. There have been several exploits patched since then.
That said, a site shouldn’t lie about not being compatible when it works just fine. Sure, maybe include some sort of warning banner that the browser is unsupported (and thus may stop working at any time), but don’t block the site.
Hence why I told you how you might be able to override it. But the warning suggests it’s only a matter of time before it will break. How, I couldn’t tell you. But new features trickle in all the time, and they may already have their eyes on one that won’t work on your browser.
They have already broken on earlier versions of Firefox. I believe the culprit has to do with the ?. operator, or part of the Shadow DOM.
Agree blocking is maybe overkill unless they know for certain some feature of that version flat breaks their site. Then again, if half their tech support calls are cured by “upgrade your browser. Wow it works now.”, maybe best to automate that triage.
But as a simple matter of testing economy, sites other than the super giant players like Google, will decide which versions they will test and maintain against. And it’s far short of "every version of every browser that’s been current in the last 10 years.
It’s a stupid waste of resources to test new features against increasingly old systems. That effort could be better spent on new features, more profit, etc.
So browser versions that are perfectly cromulent get dropped from “supported” to “unsupported” not because the site devs know their new feature X doesn’t work. But rather because they don’t know whether feature X does or not and can’t/won’t spend the effort to find out or to fix problems if they’re found. “Supported” means “we know it works because we spent the testing effort to confirm that it works.”
Browser testing is already an unholy nightmare. You have to cut off some of the Hydra’s tentacles or it’ll strangle you.