There isn't really an ELI5 version of computer architecture but you could start with the book Inside the Machine by Jon Stokes. Then you can get into SIMT.
Linux loves to leave papercuts unfixed or undocumented for decades. The solution is to build against an older version of glibc but no one tells you that or how to do it.
If you mix proprietary human-written code with uncopyrightable public domain code, the result is still proprietary. There's no reverse virality. There's no problem to fix here.
For example, every proprietary OS includes public domain SQLite and it's fine.
Memory fabs make a mix of DDR/LPDDR/GDDR/HBM and they continuously adjust the mix to market demand. If demand for HBM drops they will start making more consumer RAM.