How to troubleshoot hanging macos login

Solution 1:

Magically, this worked, but I suppose that key combination is to disable startup things I might need later.

Well, if it works w/o apps startup when login, you can use bisection to find out what app causes trouble: disable all the startups then enable just a half of them, check if issue'd arise again or not, disable them again and enable those that weren't tried. If you found which half is causing troubles, repeat same procedure with its "suspects" — also splitting it in halves. That could allow you to narrow it down to a single app that being run on startup botches the login.