[KomoD]

> or even having a user content domain.

This is the way to go, spend another ~$10/yr and keep customer subdomains on another domain.

Another option instead of doing "dave123.users.example.net" is to suffix or prefix the subdomain with something, like "zone-dave123.example.net".

[ILIWYCMBgPicCha]

Yeah, using a different domain isn't a bad idea. I had considered it, but I know slack doesn't do it. (I also know I'm not Slack).

There was a service I used some years (decades?) ago that let users choose from three or four domains that they owned. I could always do that in the future, too.