You can do su <username>
to change the user in the current shell. Afaik it just defaults to root if no user ist specified. Everytime you run su
you actually do su root
That said I always thought that it stands for switch user so intereresting to know that it‘s substitute.
I still use my Pinebook Pro as daily driver (next to a desktop pc) and I‘m actually quit happy with it. It’s not the most powefull machine but it does it‘s job.
Also I never really experimented with all the special distros. Nowadays I just run plane Debian on it and everything seems fine.