You don’t get it. Server settings are only one part of it, Discord also has their own account wide policies.
For example I had a second account I used on Discord. Verified email, used it for years on and off every now and then. Last time I tried to login? No longer possible, I need to add a valid phone number and verify it. I couldn’t even get back into the account at all!
No way around it, if Discord flags your account for whatever reason they log you out and force you to add a phone number. All it might take is you pressing logout once and next time you try to login you’re blocked. If even that.
If you want to use Discord nowadays you need a valid phone number, that’s it.
Either you agree with it and use their service, or you don’t and delete your account with all your data.
They use this to battle spam accounts (with quite some success, been over a year since I’ve been contacted by scammers), there is no good way around it.
But you can easily test this yourself: Go and try to create a new Discord account without a phone number. Then try to use it.
I couldn’t, Discord immediately forces me to add a phone number on login.
Maybe it’s regional? Or they have different behavior based on your email address provider?
I gave up on having a second account.