OK, in the end it turns out my 91.1 FM Aurora catch from 3am yesterday was NOT SWR1 RP.
I wrote to the station using the form on their website https://www.swr.de/swr1/rp/kontakt/swr1rp-mail-ins-studio-100.html
and got a reply from Jürgen Kurth, DG7KH, who could not confirm my YT recording be of SWR1 RP. He even sent an off-air recording of the station at the same time as my recording, and they definitely don't match.
So what is it? Next guess, probably the more obvious one is Antenne Brandenburg, 20kW from Casekow.
