Nothing to worry about especially if it boots fine and loads your graphical environment. It's just a grub warning message because grub doesnt play well with (presumably) nvidia. You could probably make some tweaks to remove the error but there's really no reason to bother.
The first two lines seem like they probably came from X, the old standard UI system for *nix. The last line is just saying that your 2nd partition on your 3rd disk was checked with no errors found. This is fine.
Given that the UI then starts up you can ignore these messages. They're there in case the system fails to start up after that point.
Ubuntu has gotten worse that it seams to was a few years ago. I didn't use it outside of servers. Many don't like the direction that ubuntu goes with snaps. But use whatever distro you want
When I first started learning how to Linux long ago everyone recommended Ubuntu... and I had a similar issue to the OP.
I had to dump the EDID of my monitor from a Windows machine to actually get X to recognise any kind of monitor modes
..it was an eye opening experience for a newbie.
Today, I still dont really like it for other reasons (I'd take Debian over Ubuntu any day). Call me crazy here guys but I think its okay to share an opinion without being called an edgelord for it.