IME the easiest way to check for free space is to use df.
If / or /var is nearly full you could probably free up some space by using dnf clean all then retry the update.
Having /home on the same disk as / with btrfs means that if you download a lot you can easily fill up the drive with what you have in /home and take up the space needed for the OS. Btrfs shares space in the volume with all the subvolumes that exist there.
I see that you have a 3T drive as /dev/sdb but it does not appear to be mounted anywhere.