It seems to me that you have already lost the data you need to actually do shadow recovery if you originally imported it as 8 bit. I have to believe you would need to have it imported in 16 bit from the start in order to get the same results as other programs that directly work against the original RAW files.
I believe G'MIC came out with a new version that works with GIMP 2.10. You'll have to re-install it. I haven't actually done it yet, but I would assume it's the same process as before.
It seems to me that you have already lost the data you need to actually do shadow recovery if you originally imported it as 8 bit. I have to believe you would need to have it imported in 16 bit from the start in order to get the same results as other programs that directly work against the original RAW files.
How do I make the Add New Layer, Delete Layer icon visible in the Layer panel?
what about G'MIC is not work for me gimp 2.10؟
I believe G'MIC came out with a new version that works with GIMP 2.10. You'll have to re-install it. I haven't actually done it yet, but I would assume it's the same process as before.