For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
The only other way I could think of would be to set the read and write access levels of all the elements in the group such that they all get hidden, and (I think) we automatically hide groups that have no visible elements.