Linux?

Hi, I feel like a fish out of water here, surrounded on all sides by what is essentially a windows-centric site..I am a dyed in the wool user of that other OS.. Linux, ( Ubuntu).. I am here basically out of sheer frustration..There are so many iterations of portable apps for Windows and yet Linux is lacking.
In particular I have spent days searching for a portable version of Firefox that will run exclusively from a USB..
I have an Appimage of Firefox that runs , mostly from a USB, but it still insists in writing to folders in the home directory on a PC..
I need to be able to take my Firefox, and its profile/ passwords etc with me from machine to machine.. without creating files that I need to manually remove from "Home" after a session.

I guess most of what I am looking for is just a method to permanently relocate the files that are written to "Home" to the USB..I figure even though we are talking about different operating systems here, that the basics of pointing to a new location are going to be constant.
I know that there is more than this required to make a true portable version, as it isn't great to wear out your flash drive with many many accesses by FF, but I am happy if I can sort my worries out bit by bit, and the starting point is getting everything working from the one place.
Sincerely hoping that somebody out there has exposure to both systems and can give me a clue.