So, I think registerConnectorClass with setupComponent is deprecated, see your error log:
DEPRECATION NOTICE: Defining connector classes via registerConnectorClass is deprecated. See https://meta.discourse.org/t/32727 for more modern patterns. [deprecation id: discourse.register-connector-class-legacy] chunk.f47b6dc1cc59c827db42.d41d8cd9.js:134:74065
and I’m also not sure we still tolerate the raw html, like in your footer component.
So this component will have to be refactored to modern patterns, and I’d advise moving it to a proper component as well, as opposed as where it currently lives under Admin.
To answer your other question
It’s due to the ongoing work of modernising Discourse and moving to new modern standards with Glimmer components.