Not sure. I removed Firefox. It is now a Flatpack. Did you change the Home location for Firefox? You can use the old location as HOME for Firefox. It does NOT seem like a bug.
I personally did not like the old version, as too Google-centric for me. If you want privacy, the best browser is unGoogled Chromium. The best search engine for me is mojeek.com as it does not censor your searches, and if you don't get what you want from Mojeek it comes with alternative search engines, my favourite being Brave search engine. I then get rid of Google, Bing, DuckDuckGo, eBay search engines.
I use Firefox directly from the Mozilla Repo (relatively new). And that is the normal Standard Firefox Look without Adjustments from others.
I don't know if You want to try to add the Repo (which I would understand; I didn't done it directly, too) but Mozilla wrote a Step by Step Guide. Maybe You want to take a Look on it: