It seems to me like all the portable apps on this website are for the windows OS's. I don't know if the creators of the portable apps are fans of Windows, but I would think that people would like to use portable apps without downloading Wine for Linux.
Long story short is it too much to ask to have portable apps for other OS's other than Windows?
I find that the search bar at the upper right hand side of the site can be a very useful tool...
https://portableapps.com/search/node/portable+apps+for+linux
Oh and welcome to PortableApps.com