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.
after looking and checking, I have not been able to find the WYSIWYG editor settings ...It's a paragraph tag. You should be able to turn this off in your WYSIWYG editor settings. Eg. in JCE Editor it's "Show Editor Path" option which needs to be set to "No".
Thanks for the help...Extensions -> Plugins -> Editor - TinyMCE
Set "Element path" to "Off"