quoted

I have included  a link to the mokutil [5] changes I have made to support 
this new functionality.  The shim changes have now been accepted
upstream [6].

..snip..

quoted

[6] https://github.com/rhboot/shim/commit/4e513405b4f1641710115780d19dcec130c5208f

..snip..

Does shim have the necessary features in a release?

Hi!

It has been accepted in the upstream shim. If you are looking
for a distribution having rolled out a shim with this feature (so signed
by MSF) I fear that distributions are not that fast with shim releases.

Also these:
https://github.com/rhboot/shim/pulls
https://github.com/rhboot/shim/issues

do mean some extra work would need to go in before an official
release is cut.

Hope this helps?