I use https://exifcleaner.com/
I’m thinking entropy would be the same either way as long as the files are the same size. The only entropy gain from RAW would be the larger file size.
If you use downloaded wallpapers make sure they’re not a solid color and to compress and crop them to a random size to make the data unique.
It most certainly is! I've done it myself :)
IIRC,
sudo apt update
sudo apt install snapd
snap install picocrypt
One of the things I love about Snapcraft is that it has detailed instructions for almost all operating systems, and if you go to https://snapcraft.io/picocrypt and scroll down, you'll get detailed instructions for just about any Linux OS.
BTW, you just reminded me that I should link the to snap page, I'll do that soon on the GH page and in the reddit sidebar.