The availability of the best EF lenses is dwindling rapidly. I believe most of the L Series of lenses have been discontinued from production. The EF lens market is quickly turning into a used lens market.
As far as for any EF lenses that you may own, there is a table in the owner’s manuals of R series camera bodies that lists which EF lens models are fully compatible with Movie Servo AF. Many older EF lenses are not fully compatible, but will still function is a somewhat degraded mode when it comes using the more advanced Servo AF features.
Most of the lenses that did not make the list are simply too slow when it comes autofocusing. This is also true of many third party lenses, both old and new. Canon does not support third party lenses.
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.