Just a little PSA: If you have trouble logging into Lemmy, make sure you don’t have a space after your username. I accidentally entered it with a space in the password manager and it took me longer than I’d like to admit to figure out why only the donut of horror was spinning but I wasn’t logged in.
For Lemmy, "username " is apparently something different than "username".
I had the same issue for several days until another user made me aware of this. I felt very stupid, so I am glad I am not alone with this.