if you are concerned about swap, you could run free -m or swapon --show to make sure it is mounting correctly.
dmesg -H --level=err can give you a look at system errors that have been reported. lnav /var/log will give you a very comprehensive view of all of your system logs. i like lnav because it shows errors (you can jump to past errors with shift + e and then forward with just e. same with w for warnings) and warnings in red and yellow (respectively) and makes them easier to spot. i’m pretty sure i had to install that in mint with sudo apt install lnav.
out of curiosity i tried that and got the same “drive is mounted. aborting” message as you. i did notice the following in the instructions which i didn’t follow that might have affected my run:
Running fsck in rescue mode requires few more steps. First prepare your system for reboot . Stop any critical services like MySQL/MariaDB etc and then type.
if you’re still interested in running fsck on your drive, that should be easy enough from a live usb.