you are accessing the Lemmy admin page through the official Lemmy UI, correct?

Correct.

do you mind sharing (if there are any) error logs of the Lemmy backend?

I’ve got no “error” lines, but outside of “trace”, “debug” and “info”, I have the following “warn” line :

WARN Error encountered while processing the incoming HTTP request: pan_builder: InboxTimeout: InboxTimeout
   0: lemmy_server::root_span_builder::HTTP request
           with http.method=POST http.scheme="https" http.host=blog.kaki87.net http.target=/inbox otel.kind="server" d432-40fa-a865-6690f61e11dc http.status_code=400 otel.status_code="OK"
             at src/root_span_builder.rs:16

Btw you might want to close the registrations. They are open right now.

Indeed, which is weird, because I’m sure I closed them when I first created the instance. Are settings lost during upgrades ?