For the best security, your seed should never touch an internet enabled computer, especially if you are storing it in plain text. Even although you are using a different OS, since you are connecting to the internet with that OS you have no guarantee that it has not been infected with some kind of malware. I would store your seed on paper and not on a flash drive at all, or if you insist on storing it on a flash drive, only ever connect that flash drive to a completely air-gapped machine.