@Kurt You can follow a Lemmy community from Mastodon by searching for the lemmy community in the research bar and following the account of the community (it appears as an account). For example, if you want to follow asklemmy community, you need to follow its account from Mastodon, as a regular mastodon account. All posts from the community (threads and answers) are boosted by the account of the community. However, it quickly becomes difficult to use in feeds, that's why I asked this question.
There is a bug in 2FA in Lemmy. In every implementation of TOTP, the account is not locked under 2FA until the server verifies at least one TOTP password. In Lemmy, if the user is unable to set up 2FA on his device, and quits the session, he is locked out of his account.