Heard the first time about them (ente) yesterday in a discussion about "which 2FA are u using?". Directly switched to https://ente.com/auth/ on Android and Linux Desktop and very happy with it.
Got that one too. Endless-spinners are one the most annoying stuff in the web. Please check for responses. I got a 403 (checked the network debug tag), probably session/csrf-token timeout...
Going to give this a try...