> I recommend learning a bit about how your filesystem works and why it can't find linked files from within an archive. This is essential computing knowledge.
Really? Is that _really_ essential computing knowledge?
On macOS, you download a disk image, then drag the icon into the application directory. Many publishers include a shortcut to the application directory and a background image with an arrow and instructions. It's primitive, but it works, and hasn't needed to change in like, 20 years. It requires no knowledge of linked files, or even what a disk image is. Drag and drop. Done.
If you can't install an app like that on most Linux distros (I don't think I've ever seen that), then Thunderbird probably shouldn't suggest that as an option. I've moved away from using Linux as an everyday OS because all these little usability things add up and suck too much of my time.