At this point I think the feedback loop is unstoppable: The lower Firefox's marketshare gets the fewer developers test their pages on it, the more pages don't work on Firefox, pushing more people to Chrome.
For my day to day use everything works fine. I don't remember anything that didn't except the vscode.dev thing that appeared in the front page yesterday. Apparently the local file access is not supported/enabled in Firefox yet.
And when I was messing with CSS a few months ago there was... background-blur? Or something like that, not supported in Firefox. But pretty minor things.
Don't remember anything else where I had to switch to chromium lately.
I also have to use Figma on a daily basis and the there are some odd things happening in Firefox that don't appear in Chrome/Edge.
And this is not an isolated case... Each time I've had to submit a complaint about issues encountered while using a webapp / website (including for payment systems, utility companies, local government, etc.) I often get the same response: "try it with Chrome" or "we support only Chrome".
I still remember the "works best with Internet Explorer", which then changed to "works best with Firefox", and now it seems "works best with Chrome"... :)
Mostly, it was horrible old sites that were designed for IE.
Of course ymmv