What is the first-time password?

[wibble]

This information does not work for me. I this is what I get for uname -a:

Linux pine64-pinephone 5.9.1 #2-postmarketos-allwinner SMP Mon Nov 2 09:26:33 UTC 2020 aarch64 Linux

neither root nor 123456 are the root password or sudo password for user.

So far I was only able to set the disk encryption password, the SSH password, and the ssh user, but I am not able to install anything because I'm missing the sudo or the root password.

If you're using password authentication for ssh it should be the same for sudo. I think PostmarketOS is one where root doesn't have a password you can use