For GParted version v1.2.0 and above (Ubuntu 21.10 and above)
exFAT support was added in version 1.2.0 of GParted. To use exFAT you must install the exfatprogs package (and NOT exfat-utils). Installing exfatprogs will uninstall exfat-utils.
There is also a requirement fo util-linux v2.18 and above. Ubuntu 21.04 is already at util-linux v2.36 so this isn't an issue unless you're manually backporting.
As of writing, GParted 1.2.0 is not yet in any version backports.
For GParted version below v1.2.0 (<= Ubuntu 21.04)
In View->File System Support, exFAT currently doesn't have support in gparted (0.28.1) for anything other than moving or copying.
No "required software" is listed, so it doesn't (yet) know about exfat-utils.
However, because:
- the partition is a valid partition, and
- its perfectly safe to move or copy (since the internals of the filesystem are not affected by a move)
the partition must be listed in the list of filesystems, but greyed out in this context.
If you must format a partition as exfat, then you can use gnome-disks
(a.k.a. "Disks") as in this question: GUI tool for formating to exFAT