Cannot Create SwapFC on non-root Drive about systemd-swap HOT 2 CLOSED

You're using the old bash script version of systemd-swap. I'm not sure if this works in the Python version, but you can try that one if you're still interested.
I can see that it's trying to create the parent directory, but that fails already. Since there is no error reported for the actual directory, I'm going to assume that it's a btrfs volume because the output of btrfs subvolume create "$swapfc_path" is redirected to /dev/null. Otherwise, we'd probably see another mkdir error. Honestly, no idea what's actually happening there.
I'll close this issue. Feel free to open another issue if it also happens with the current version.

from systemd-swap.

A okay, I think I installed through the package manager, it's on 4.3.3. I'll try cloning and building the deb and see. Thanks :)

from systemd-swap.