For encryption without having to know much about it, then using the
TAILS product may be the easiest Linux solution. On the USB drive that you install TAILS on, it offers the ability to create a data persistence area. They
claim, "The persistent data is stored using strong, well-known, Free Software, peer-reviewed encryption tools (dm-crypt and LUKS)". However they do have a few things they want to
warn you about.
With the small physical size of USB drives these days, then, under duress, you could put it in your mouth and swallow it. This may result in some delay and reduce the enthusiasm of someone trying to decrypt your data ;-)
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I notice with my Ubuntu Mate 18.04.2 if I open the Caja file manager and right-click on a folder then in the pop up menu there is the option to "Encrypt" the folder.
I from what I vaguely recollect from looking into this home folder based encryption on Linux a while ago the meta-data of the encrypted files off the folder could still be obtained. Thus although someone might not know the passphrase and be able to decode
your data, they could see the names of all your files. So it might be better to have file names like, "a_guide_to_growing_pansies" than "where_i_buried_the_gold_bars".
There was also
discussion that the current form of home folder based encryption (fscrypt) was being phased out and its replacement (ecryptfs) had bugs and wasn't ready yet. The interim solution was to use volume based encryption.
cheers,
Ian.