I've had it happen on servers where that moderation option is not enabled. My worst experience was trying to join a friend group's discord via an invite link shared with me. I was prompted to create an account with email, and I did. I was then shown a read-only view of the server: I could see all messages and other folks could see I joined and 👋 to me. I could not send messages myself, however, without verifying with a phone number. Further, I couldn't use a Google voice number (my primary number) to verify, nor my "real" number which was associated to another account.
Sometimes it depends on discord itself finding you suspicious, for some definition of suspicious. perhaps a user agent whitelist? lack of Google cookie?
it's awful and I hate it. I generally prefer not to have a shared identity across communities, and there's no way to create a usable discord identity without a phone number.
Why do you need to back up that server data? The great thing about joplin, is that the full content of your notes (and history) is distributed, like a git repo. As long as you have one device left with your notes, everything else can be bootstrapped from there. If your sync server burns down, start a new one and sync your notes to it again.
I've had it happen on servers where that moderation option is not enabled. My worst experience was trying to join a friend group's discord via an invite link shared with me. I was prompted to create an account with email, and I did. I was then shown a read-only view of the server: I could see all messages and other folks could see I joined and 👋 to me. I could not send messages myself, however, without verifying with a phone number. Further, I couldn't use a Google voice number (my primary number) to verify, nor my "real" number which was associated to another account.