I think your read on what people typically do with Plex probably doesn’t align with reality. I also think in the end you’re way less optimistic about the potential of open source software than I am. There are multiple areas where OSS options are either dominant or very competitive, but I am also clearly way less picky about how that gradient of openness to commerciality than you are. We can agree that it’s fine that there are options for both or all steps in that gradient, but there is a ton of snark and all-or-nothing attitude in that community as well.
I will say that If you have a commercial option like Plex and a couple of open alternatives (say Kodi and Jellyfin for the sake of argument) I would prefer one of those to have the type of UX that can compete with the closed commercial product because you can compete with open alternatives.
It’s a fair question to ask why you were using MS Authenticator in the first place, but if you have to use it for a work thing I’m not isue if it will export to other TOTP alternatives or not for Microsoft account stuff. Does anybody know for sure?