I expect that as opposed to the Raspbian distro's way, you run NFS(4) by default?
I'm currently in the process of setting up a pi 3B+ as a NAS, & have struck a problem trying to automount the NFS share on MX. This is due to the raspbian using NFS3 by default (on a 4.19 kernel!?).
It mounts fine from the command line if I use the following in the command line:
mount -t nfs -o nfsvers=3
After trying to call the mount in MX via fstab (variety of ways), /etc/rc.local , various "bash" system files, & other methods too, I am obviously now looking at what I can do to make the pi better - even though raspbian has presented me with no problems before now...