Sorry to jump into this discussion, I have a checkmk agent 1.5.0p24 installed on a RHEL 7.8 server which has glusterfs setup:
$ rpm -qa|grep gluster
glusterfs-api-7.5-1.el7.x86_64
glusterfs-fuse-7.5-1.el7.x86_64
glusterfs-libs-7.5-1.el7.x86_64
glusterfs-client-xlators-7.5-1.el7.x86_64
glusterfs-cli-7.5-1.el7.x86_64
glusterfs-7.5-1.el7.x86_64
glusterfs-server-7.5-1.el7.x86_64
And without doing anything, I see the basic filesystem and mount options check being detected:
However, if the question is about to monitor glusterfs as a whole, then please ignore my comment.