Encrypted offline backups

Just out to get some feedback and input.
if i would like to have an offline (like USB thumb-drive) backup of some important data, what is the best solution. Or is a good safe to store it in better?
i would like to be able to decrypt the data whiteout any special software i get dependent on (like linux or so is of course ok), or is the thumb drives with built in encryption any good?

i know Tom uses offline backups on thumb drives but not sure if they are encrypted??

just want to get some suggestions on good ways.

For any external USB drives I use LUKS which is native to Linux.