@richardjhurst
as an emergency you can always disable OpenCore and Mojave should work normally.
just remove the disk with the OC EFI partition.
to go back to catalina you must repeat the blessing in recovery.
about the help: in your config.plist find
Code:
<key>Kernel</key>
<dict>
<key>Add</key>
<array/>
and replace as described above by
@cdf
if you dont know how to do that, read the part about "Advanced Configuration" in the
guide
and by the way... if you connect by cable there is no problem with mojave