

Maybe that’s specific to UK? I’ve never had to upload ID at any of the general domain registrars but am not in the UK. Maybe you’re looking for a registrar that doesn’t do that for UK residents, specifically. (or you might need to use a VPN or something, dunno)
Privacy aside most people tend to buy a domain at the cheapest registrar (keeping in mind whether to renew at that registrar later or transfer out to a new one when the time comes). There are domain registrar sites people use for comparison, been a bit since I’ve needed to shop around but sites like https://tld-list.com/ can be helpful. You could try doing a lookup there and work your way down the list until you find one you like.
Or if you’re really set on looking for a service that actually advertises no KYC then looking through this list may help https://kycnot.me/?categories=domains (njalla is one of the listed ones there as someone else mentioned).
Jelllyfin + Subfin (https://github.com/williamkray/subfin-plugin) works well, I’ve been using it with the OpenSubsonic Android apps listed in https://www.navidrome.org/apps/?platform=android&api=opensubsonic without issue. e.g. Substreamer, Tempus, Airdrome, etc. all work fine with Jellyfin + Subfin.
I’m guessing you’re not on Android or iOS since Jellyfin has apps on those platforms - but you should be able to use any Subsonic/OpenSubsonic app once set up with the plugin.