I'm trying way too hard to use Firefox. I have a fresh install of Catalina, I installed Firefox and I've got the same issue as I had with Mojave, Firefox doesn't save visited websites. The strange thing is, I visited Firefox.reddit.com for more information, didn't find it, but Firefox.reddit.com now works with autocomplete. Prior to visiting Firefox.reddit.com I visited reddit.com, and it does not autocomplete. This is rather annoying issue. In both Mojave and now Catalina I did check the databases, they were both working "fine" according to Firefox, deleting the databases does not fix this issue. There are no weird settings blocking autocompleted history.