lemmy-1     | 2024-03-04T00:55:02.006942Z  WARN lemmy_server::root_span_builder: Unknown:
lemmy-1     |    0: lemmy_apub::insert_received_activity
lemmy-1     |            with ap_id=Url { scheme: "https", cannot_be_a_base: false, username: "", password: None, host: Some(Domain("lemmy.world")), port: None, path: "/activities/announce/like/19396dee-b18d-42d4-ba74-31986d4726e0", query: None, fragment: None }
lemmy-1     |              at crates/apub/src/lib.rs:198
lemmy-1     |    1: lemmy_apub::activities::community::announce::receive
lemmy-1     |              at crates/apub/src/activities/community/announce.rs:153
lemmy-1     |    2: lemmy_server::root_span_builder::HTTP request
lemmy-1     |            with http.method=POST http.scheme="https" http.host=biglemmowski.win http.target=/inbox otel.kind="server" request_id=13f38a7a-8814-4350-bf3a-b5a7e1dd3906
lemmy-1     |              at src/root_span_builder.rs:16
proxy-1     | XX.XX.XX.XX- - [04/Mar/2024:02:55:02 +0200] "POST /inbox HTTP/1.1" 400 47 "-" "Lemmy/0.19.3; +https://lemmy.world"

Considering the timing this is probably a side effect of .world upgrading to 0.19.3 and their federation kicking into "higher" gear. I see 20-50 warnings like these in logs every minute all from lemmy.world.
I am guessing .world thinks at least one of my users are subscribed to a community but they are not (?) so my instance drops the federation (?)