@linux-aarhus I’ve just installed udev-usb-sync v1.1-1 on my Testing branch machine, which is running kernel 7.0.0-1-MANJARO, and it seems to be working as it should be.
I tested it by downloading a ~1GB video file to my WD Elements external drive, and also by saving 30 images (each ~10MB) to the external drive via Firefox’s Tab Image Saver add-on. The writing speed was good, and there were no other issues encountered.
So it looks like the udev-usb-sync issue with linux70 has been resolved.