Most catastrophic scenarios I can imagine result in loss of advanced silicon production, but not necessarily all silicon production. More likely than not there would be ways to keep fabs for old well-trodden processes running. In that situation, there’d probably be a temporary shock of no computers followed by new computers being a lot less powerful… it’d be less “no more computers” and more “new computers are comparable to their Pentium 4/PowerPC G5 era counterparts”, in which case operating systems would still be graphical, just a lot more lightweight. Linux and BSDs would probably quickly take over desktop computing due to being able to run reasonably on such systems with minimal legwork.

If we can’t manufacture chips at all, yeah, things will be in enough of a pickle that computers will be the least of our worries.