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
See Announcement
We are still working on the Joomla update.
Which Joomla template are you running? Did you try with the standard "Protostar"?A Joomla template that Supports the bootstrap framework
Memory limit is a good hint, but your system information is showing only 24M!! (System Information/Php Information, search for memory_limit)The memory limit is now 128Mb