As I recently mentioned, Devise has been finally patched to work with Rails 7 out of the box.
But when I tried installing it, I had a few minor issues:

• remember to use MAIN branch of devise
• re-generate the devise.rb initializer, or add these lines to it:

  config.responder.error_status = :unprocessable_entity
  config.responder.redirect_status = :see_other

Episode source code with comments: https://github.com/corsego/112-rails-7-devise-patch/commit/4717a4a6e12bb292b5515e97ce980d0c17751af7#
The devise patch: https://github.com/heartcombo/devise/pull/5548

0:00 Devise Drama queens
01:00 Install Devise
2:21 Check if Devise works (it doesn't)
2:46 Make devise work (add config.responders)
5:10 Link to sign out
5:43 Summary