Inga stands with 🇺🇦🇵🇸 on Nostr: nprofile1q…eqfh3 as for the second request, once again IANAL, but this seems to be ...
nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqsh47jfjwrysr250kn24natwhnq8dhdguc9dswnp0ey8alsdh389qneqfh3 (nprofile…qfh3) as for the second request, once again IANAL, but this seems to be ActivityPub Inbox URL your instance tells everybody to use for this account (I cannot say for sure because your instance rejects unsigned requests to the actor JSON, but this is the Inbox URL my instance displays after it fetched astrobin_iotd profile).
So some (any?) federated interactions with astrobin_iotd on your instance will go to this URL, this is just how federation / ActivityPub works. In this case this was apparently about an interaction (a follow request?) from mastodon.sdf.org.
Why is your instance rejecting it with 500 is another question. Why you see this request repeated again and again is very clear; mastodon.sdf.org will try to deliver this activity again and again until your GTS server will finally accept it or reject it or enough attempts / time pass that mastodon.sdf.org will mark it as undeliverable, and will mark fedi.stfn.pl as having federation problems.
So some (any?) federated interactions with astrobin_iotd on your instance will go to this URL, this is just how federation / ActivityPub works. In this case this was apparently about an interaction (a follow request?) from mastodon.sdf.org.
Why is your instance rejecting it with 500 is another question. Why you see this request repeated again and again is very clear; mastodon.sdf.org will try to deliver this activity again and again until your GTS server will finally accept it or reject it or enough attempts / time pass that mastodon.sdf.org will mark it as undeliverable, and will mark fedi.stfn.pl as having federation problems.