And I do wish I had checked on this sooner. The newer Canon L glass now works with it. Still no joy using any of the teleconverters, not at night for lunar or planetary photography. It doesn’t quite focus when using teleconverters at night. Will try again in the morning to see if brighter lighting conditions allow the use of them.
But here’s the results:
OMD EM1 with Kipon EF to MFT adapter. Lens mounted, Canon 100-400mk II L IS
OMD EM1 Kipon EF to MFT Adapter, Lens mounted Canon 70-300 L IS