I installed darktable version 2.4.3 in windows 10 newest release in 64-bit machine and had exactly the same problem. All mein photos are on E:, an internal drive. So I deinstalled the version 2.4.3 and installed version 2.4.2 and look: I can now import files from every drive on my pc. It looks to me, that a part of the code has been lost. Now I hope, that the developer will find the code or what ever the bug may be, because darktable seems to be a very good software to me.
Many thanks in advance.
best, carlo13