If I have updated my PGP key, I can't upload it. An attempt is rejected as the key is considered a duplicate. But a PGP key is a sequence of OpenPGP packets, each of which can be an update. It's very legitimate to update a key: very commonly, to extend the lifetime of a key by giving it a new expiration date.
In my case I was trying to add some new notations used for other purposes so I'm not facing a deadline right now, but fixing the key handling would be nice. :)
As a workaround you should be able to remove the key and then upload the new one.
I could, did I not have encryption enabled for messages. Too much hassle to bounce through disabling, deleting, re-adding, enabling message encryption and whatever I just missed there, so I ignored this "nice to have" update and filed an issue in the hope that it's available functionality by the time it matters for me. :)
FWIW, last year I noticed that with two keys, I could switch which one is used for encryption without all the other choreography, so was able to delete/add-back the fallback RSA key, switch to that, delete/add-back the Ed25519 key, then switch on /privacy again.
This year, your logs got an Internal Service Error from my doing this, because I didn't reload the /privacy page before trying to save back onto the main Ed25519 key. To my mental model, it feels like there is a reference to an internal identifier for the key generation, so despite the key with that fingerprint existing at the time of the save, it would have been in a different internal object on the sr.ht servers. Reloading the page was sufficient to pick up the correct identifiers (7257 and 7258?) and it did save.
So I still have a functional workaround and sorry for the log-noise.