I did try to signup over a custom oidc but everytime i do get the following error, also i put all configs below so you could take a look at it. Hope it can fix it.
(i did replace for security my e-mail domain with example.com and also some ids with an X)
Due to new user forum limits i was forced to but all confs in a pastebin. sorry.
Last but not least, in Auth 0 i just added the ,mentioned callback url from tailscale, i paste it not here because this should be right
Lovely / Best / Wonderful Regards