Ok people, I spent 4 hours researching and trying all the solutions out there and finally found a fix that worked for me and wasn't mentioned in any of the answers submitted. First of all, my machine is a mac mini 2018, 1TB ssd, 64GB of ram, i7 processor. Latest Big Sur MacOS version. You will need an additional Window PC at hand. What I did: 1- Installed APFS for Windows app from Paragon ltd on my PC. 2- Connected my external SSD and mounted it: which makes it now able to be read from and written to from my PC 3- Just explored the content through my window explorer browser: Opened a couple of folders, 2 or 3 levels down. 4- Unmounted it(I think this is quite an important step not to be skipped as Windows usually allows us to do that without issue but I suspect that the unmounting process somehow participate restoring the drive registry to a format that Big Sur will now be able to detect) 5- Connect the drive to the mac: It should now be detected and work as usual. Hopefully this will save time and a few tears to some people. Nothing else worked for me. Best JG