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
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You said you set the collation on the table, but did you do so for the FIELD? And notably the field which stores the label?I have modified the collation of the table to utf8_unicode