black screen with white spinning wheel after High sierra login Thank you in advance for any useful hints.
After login I get a totally black screen or one with a spinning wheel.
I have tried the following things.
Zap nvram
Smc reset
Deleted as single user login peers.
Start as another user that was installed for migration
Verbose mode... too fast to read and ends up in the same thing

Did try shift ore safe mode.. same result. Shift makes No difference to the boot process

Started into recovery mode which doesn't want to let me repair my disk. The stupid High Sierra installation made it encrypted. Can't remember that it asked me.. it was certainly not that I wanted it.

I had restarted because Lightroom kept crashing

I have been struggling for 8 hours now and I am at wits end

NO. there is no other working mac and internet installationis not possible because I am on a 3g phone line in rural Costa Rica

There is only 1 thing that works.. the useless guest login boot into Safari mode
You could try creating a new user account by tricking the computer to going through the initial setup process.

Instructions on re-running Apple Setup Assistant

By creating a new user this way you can check that the issue is specific to your user account, and not your installation of macOS. If this account can login you could copy the files from the other user and the issue is resolved.

If not then you need to find a better internet connection and reinstall, someone could download the files onto a USB stick for you perhaps?