Unable to login - need to boot into single user and recover password?

A week ago I installed Xubuntu (20.04?) on a Dell Latitude e6530 that had Windows 10 "ready to install" (I never agreed to MS terms, so didn't activate). I was the only user and had root access and (I'm assuming) superuser rights.

After installing Wine and Scribus and learning some how to navigate the system, I changed my password, set to No Password on Login, and noticing I wasn't an administrator, made myself one. I then closed lid (thinking that would put changes into effect - doh!), and once I opened lid, was prompted for a password, which was not accepted - neither the new one (which I uncharacteristically had written down) nor the old.

With help from Ask Ubuntu folks, I made it to the Grub (2.04) prompt to get into recovery mode. There I got stumped. Didn't know which to choose: Linux 5.4.0-96-generic or Linux 5.4.0-42-generic. The -96- appears to be more recent than my Xubuntu (if it indeed is 20.04 from April 2020). So I'm guessing I should edit the -42- one. [Dunno if using the wrong one will screw things up (even more).]

Once I get to the right recovery mode, and am presumably able to boot into single user mode, how do I recover my password, if that's what I need to do? And should I un-administrator myself?

Or perhaps I should cut my losses and reinstall the whole salami. After all, I don't understand most commands others have kindly offered; I don't think blindly following (anything or anyone) is a good idea.

Thank you one and all for your gracious support, including the (staffer?) who sent me a Yes/No query whether any of 16 suggestions had helped/resolved my issue. All I could answer is "not yet", but that wasn't an option, so I've been silent to that query so far.