I don’t see other ways of fixing the G’MIC for GIMP 2.10 problem than recompiling the plug-in specifically with the GIMP 2.10 API, with all the new libs, etc.
On Windows, this means : setting up a new compilation environment for GIMP 2.10 plug-in, which is a pain to do (only a few people know how to do this cleanly, like @samj or @partha) .
The solution will come from them probably.
Personally, I’m pretty sure this would take me ages to make it work by myself (and as I said in a previous post, I’m currently very busy writing a manuscript for a University degree).
I guess we have to wait then 