Linux Mint has an eject button that allows any cached writes* to finish, prevents new ones from starting, and un-mounts it. It’s actually important to use the eject button as flash drives are slow, and the write cache can obscure the fact that a file isn’t done writing yet.

*Copying a file will add it into the write cache while it writes out to the disk. As soon as it is in the cache, you can use the file as if it was already done copying, including making changes.