Oh. My. God… That . Was. HARD!
There are a great many tools out there for making panoramas (big, long photos, covering a large number of degrees of field of view). So many, in fact, that I won’t even bother trying to link to them, not even the (very large number) of ones that I used in the end.
Suffice to say that getting a complete set of free tools with which to make panoramas is anything but simple. Getting such tools for Linux and making them work is so hard that it beggars belief.