File transfer issues Windows 8.1 <-> FP2

Since upgrading to Android 7.1, I have more troubles than ever to transfer files between my Windows 8.1 PC and my FP2 (Stock OS, but without Google services). Here is a list of methods I tried and the issues I have. Maybe you can give me some advice on what I could try.

USB Transfer: Doesn’t work at all. Windows only sees an unknown USB device, driver update doesn’t do anything. With Android 6.0, I could at least use photo transfer, and I could also transfer non-photos by putting them in the right folder.

SD Card: I can read/write the SD card on Windows, but I can only read the SD card in my phone (Amaze and Ghost commander). That means I can transfer data from PC to phone, but not the other way.

Bluetooth: I can send files from the phone to Windows, but not the other way. Windows just says that something went wrong, and the file transfer failed. The devices are paired.

Have I left out any standard option?