stalebrim: Holy crap, it worked. It actually worked. Now my Solus is running on XFS too. Now I can finally de-duplicate the files on my disk!
However, because I'm running a BIOS system instead of a UEFI system, I did have to reinstall GRUB after deleting the original EXT4 root/boot partition, since the bootloader wasn't on a separate VFAT partition. Wish I'd thought of that before rebooting...but at least I was able to boot from a USB thumbdrive, chroot into Solus, and reinstall GRUB that way.
Anyway, thanks for the tip. Any idea if the same process works for migrating to BTRFS also? I know snapshots don't play nice with kernel rollbacks, but rolling-back the kernel is far less useful to me than rolling back stupid mistakes I made in userland.
