It’s worth pointing out that a lot of those “weird” old chips weren’t formally supported anyway, and the the fact that the software worked on them was a convenient fluke, and by design or intention.
This is the magic of Linux so far to be so versatile and able to support so many hardwares.
But that being said, most of the time, issues are not coming from really exotic "chips" but from little variations, configuration or system library versions.
Let's say you want to cross compile from x to y, and want code to use that specific memory space. This is when things start to get messy usually.
Example of how you can lose a lot of time and get crazy, when you just wanted to compile the code of something for your case:
