Very simple cross-platform file encryption … https://www.tromjaro.com/cloaker/
Cryptomator
Free client-side encryption for your cloud files.
Open source software: No backdoors, no registration. … https://www.tromjaro.com/cryptomator/
VeraCrypt
VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux. … https://www.tromjaro.com/veracrypt/