Following RSS Feed is broken

Steps to reproduce

When i try to add a new RSS-Feed to my following channels i get an error.

1. Go to "Channels"
2. Add new Channel
3. The form is almost emtpy
4. Insert an RSS-Feed Link and click to "follow"

What happens?

Nothing happens except the errormessage in frontend. No output in server-logs.

What is expected?

Add an RSS-Feed of a podcast to my channels

Context

Funkwhale version(s) affected: 1.2.0

Firefox Linux 91.4.1esr Instance is non-docker with nginx as proxy Frontend is build with https://dev.funkwhale.audio/funkwhale/funkwhale/-/jobs/81069/artifacts/download because download of 1.2.0 gives error 404. Its a workaround from Matrix-Room https://matrix.to/#/!LfWevXYWdhwVFvDXRf:matrix.org/$1640707497755522wMvAS:matrix.org?via=matrix.org&via=tchncs.de&via=converser.eu