If you are using a service for work, you should not be expected to maintain a direct relationship with them. It's on your employer to negotiate account creation, terms of use, payment, banning or whatever else. This is exactly how something like, say, Slack works.
you can also use GHE with unmanaged accounts that are still connected via SSO for approving access.
using enterprise managed accounts and unmanaged accounts on the same system can be quite annoying because you'll need to use different browser contexts (container tabs, separate browsers, etc.) and also different hostnames for ssh cloning to use different ssh keys.
https://docs.github.com/en/enterprise-cloud@latest/admin/ide...
https://docs.github.com/en/enterprise-cloud@latest/admin/ide...
(That was 12 years ago I haven't checked if https/oauth made things better)