Definitely something weird going on for me, too. Have used custom camera profiles (Lumariver Pro) for years, am used to them being elements in capture import presets. So today I created a new LR catalog specifically for one shoot, loaded a Develop preset that included camera profile (Fuji XPro 2), but when the import completed all files used Adobe's generic "Color" camera profile. Not only that, but when I go to Develop module to try to associate correct camera profile (the one that is supposed to be part of the Develop Preset for import), no profiles listed other than Adobe's. When I activate the Profile 'selection' pallet, there is no "Browse" button as before; and just as you found...
no - if I try to import the profiles I want I just get a message saying that they're already imported.
So I opened another LR catalog - one I've been using for years, and the whole camera profile section behaves just as it always has, with none of this disappearing profile stuff. Quite bizarre.
Now I'm curious to see what happens after I get home & import this LRcat into my existing LR catalog.
No idea if any of this might be relevant, but specs are MacBook Pro 16 (M1-Max) running OSX12.2.1 Monterey, LR v.10.2 (haven't updated since catalog work happens on an older MacPro stuck on Mojave)
So I guess it's not just you, pflower...
John