URL MTg Arena update 64
A simple fix that's quicker than completely uninstalling and reinstalling the entire game is going to the Wine prefix directory and do this:

cd "$WINEPREFIX/drive_c/Program Files/Wizards of the Coast/MTGA"
rm -rf version MTGA_Data/[E-z]*

Then restart MTGALauncher.exe.

This has worked with update problems in the past, and it worked for me this time.