supported filesystems

-t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
The programs mount and umount support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. It's recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated).
If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. Mount uses the blkid library for guessing the filesystem type; if that does not turn up anything that looks famil‐ iar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent.
The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module au‐ toloader.
More than one type may be specified in a comma-separated list, for option -t as well as in an /etc/fstab entry. The list of filesystem types for option -t can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry.
The prefix no can be meaningful with the -a option. For example, the command
mount -a -t nomsdos,smbfs
mounts all filesystems except those of type msdos and smbfs.
For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the de‐ sired call.

pi@buster48:/proc $ cat /proc/filesystems

nodev sysfsnodev tmpfsnodev bdevnodev procnodev cgroupnodev cgroup2nodev cpusetnodev devtmpfsnodev configfsnodev debugfsnodev tracefsnodev securityfsnodev sockfsnodev bpfnodev pipefsnodev ramfsnodev rpc_pipefsnodev devpts ext3 ext2 ext4 vfat msdosnodev nfsnodev nfs4nodev autofs f2fsnodev mqueue fuseblknodev fusenodev fusectl