About a week and a half back, Jerboa on the Play Store received an update that added 0.18 support and started displaying a similar message whenever you logged in, but didn't actually block using the app or posting, but certain features were not working correctly.
As of the update yesterday, Jerboa crashes unceremoniously if you happen to be previously logged in on lemmy.blahaj.zone, and prevents fresh login with the message above.
I'm a bit worried about how the Jerboa devs are handling updates ☹️
Yeah I really wish they added litterally any backwards compatibility :/
You can read my other comment here if you want to downgrade the app until blahaj.zone updates: https://lemmy.blahaj.zone/comment/438116