Ok, it's not in the Application folder so it's gone. The setup should at least ask if files are to be removed after install :(

For the encryption I don't have FileVault enabled, checked with this via SSH: fdesetup status says "FileVault is Off."

no I can't add a new user, setup assistant is stuck on language selection, spinning wheel there too :(

For the encryption thing I don't think this is the problem, this is why: I have an older macbook and I'm using it to access via SSH to the one with Big Sur, while in SSH I can see all the files in my user folder. I was also able to enable root access and su to root. I've attached my time machine disk and the commands to do a backup are also working. Seems something went wrong with the Big Sur update. After finishing instead of going to login screen It was rebooting and rebooting forever, it went to login (not working) only after turning off and on the MacBook

for setup assistant I mean this: cd /var/db mv -i .applesetupdone .applesetupdone.old and reboot, with these commands at boot the mac shows setup assistant, some suggest it to create a new user

Is it possible to read the messages of verbose boot via SSH? I tryed reading live on the screen but in retina display that small text quickly scrolling is unreadable

I see this error in system.log: Jun 9 09:24:44 MacBookPro-2 efilogin-helper[514]: objc[514]: Class EFILWLogging is implemented in both /System/Library/PrivateFrameworks/EFILogin.framework/Version‌​s/A/EFILogin (0x7fff81cfc910) and /System/Library/PrivateFrameworks/EFILogin.framework/Version‌​s/A/Resources/EFIRes‌​ourceBuilder.bundle/‌​Contents/MacOS/EFIRe‌​sourceBuilder (0x1097ed078). One of the two will be used. Which one is undefined.

@Jean_JD yes, problem is not I can't digit password, but password is accepted then I get ethernal wheel spinning

@Jean_JD Yes, tryed both things but didn't work