Error installing Big Sur

Force Shutdown computer via Power - Touch ID Button ( both are the same button ). Disconnect all external drives. Connect to charger. Restart and Immediately hold - Shift - key. This is Safe Mode and will do a Repair Disk, Clear cache files and only load Apple Software and Fonts. This process will load much slower - Norma. If all goes well - it may or may not allow the upGrade process to complete. If it does complete - Setup Assist of Big Sur will be presented.

Can it boot to Recovery Mode - Command + r - immediately at startup and run Disk Utilities to see the Storage available?

Second to last option - Revert your Mac to a previous macOS version this involves recent Time Machine Backup.

If this does not work - advise and offer an option but it will involves loosing everything on the computer and can not be restored.

If your Mac starts up to an Apple logo or progress bar

If this does not work - you may have tries to install and Not Had Enough Empty Disk Space. If that proves to be correct - it will present a different and involved solution

User wrote " I try to use Apple ID to login, it comes up with "error connecting to Apple ID server" is because when booting into Recovery Mode - special attention to Wifi Icon appearing - must Manually Input Wifi Password.

Sounds like there could be a problem with your computer, but if anyone can help, it’s P.Phillips. Good luck

Is there a way you can skip the update? Or is it stuck in an endless cycle?

Unless someone else has something you’re probably out of luck. If you have enough to buy a new mac, do that because windows computers are trash.