Interesting idea, hadn't really considered the standalone concept. Is the desire for a self-hosted portal related to privacy? If so, the extension doesn't store any data, but if you want full assurance, you can self-host the API that's in the repo [1] and install the unpacked extension yourself [2].
More-so thinking of the ease of use rather than privacy, but that does play a role here. Specifically the ability to switch between devices or browsers, or maybe use this on ORG managed devices that don’t allow installing additional software on.