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.
I just committed this, which should allow you to specify reply to email/name, and it'll use the J! config values if those are left blank.
https://github.com/Fabrik/fabrik/commit/f2f5bd840fe429da5cc9f5f8614f48d90bf1e67f
There isn't a way of attaching files. I might be able to add that, perhaps as an option to check for fileupload elements, and optionally add files from those. But that would probably be something I'd have to bill a little time for, as it wouldn't be as quick and easy as the reply-to stuff.
-- hugh