OS will not mount the VM partition. Virtual memory must be forced to work

Solution 1:

Solved. Cobbled together a workaround with information from interwebs.

Created this plist named “local.mountdisk1s4.plist” containing:

Label local.mountdisk1s4.plist ProgramArguments /sbin/mount_apfs disk1s4 /private/var/vm KeepAlive SuccessfulExit

Placed it in /Library/launchdaemons

Swapping now works as it should. Still not sure how this all broke in the first place, or if there's a more elegant solution.