I've had this issue since the first day I started using linux about 15 years ago. Always the same issue, transfers start fine and slows down to a crawl, only on USB sticks.

The USB sticks are fine, I can make bootable sticks in five minutes but if I copy a file of similar size to them is half an hour and then five to ten more minutes waiting to be able to safely remove the drive.

There are dozens of forum posts, some blaming the drives, others the GUI, dirty buffers, outdated kernels, fastboot for some reason. Others marked as solved without a solution because it magically solved itself.