Domain transferred to Registrar, UI still asks to update nameservers

I have exactly the problem as in Transfer to Cloudflare Registrar completed, now asking for a nameserver update.

I transferred a domain to Cloudflare registrar, but something seems to have gotten confused.
I was instructed via email to update my nameservers, which I can’t, as Cloudflare Registrar should automatically use the correct ones, as I understand it.

I already opened ticket 2260821, as I suspected a bug in the system, but that got autoclosed, and I was pointed to here, where I found the thread linked above, which in turn was closed with instructions to open a ticket.