Can't log in with any user after trying to reset root password and can't get system mounted writable

[SMG]

Hi,
I am using openSUSE Tumbleweed.
I tried to reset my lost root password via the instructions here: https://www.thomas-krenn.com/de/wiki/Linux_Root_Passwort_wiederherstellen and later https://en.opensuse.org/SDB:Recover_root_password
Meaning, mounted as read-only in the end.

After rebooting, I could not log in as root nor as a normal user, not on TTY1 or TTY2.
I logged into the INIT=/bin/bash shell again, and set root and all subvolumes to rw, but that did not help.

Rolling back to a previous snapshot works, I am immediately logged in as the normal user. But the root password is not changed in this case and the system is at least partly in read-only mode, e.g. NetworkManager complains that the system is read-only. I cannot test creating files on root because I don’t know the password, but I can create files on /home. I cannot remount anything as writeable for the same reason.

What did I do wrong and how to I fix this? Thank you for any help.

[myswtest]

Since I retired about 4+ years ago (forgetful at times - an aging thing), I’ve written the root password on a piece of paper that I’ve hidden away in well-known places (hopefully I remember where that is).

But, in the past, I’ve successfully used this to recover the root password. It uses slightly different commands and order.

https://support.scc.suse.com/s/kb/How-To-Recover-the-Linux-root-password-1583239288864?language=en_US