A while ago I accidentally fried the EEPROM containing the BIOS in my #NuXT (IBM #PCXT compatible) machine.
I finally got around to dropping in a replacement, but also wanted to upgrade it at the same time.
At first the machine wouldn't boot and it took me a long time to realize a bug had been fixed in a later BIOS revision, requiring a wipe and reinstall of MS-DOS. A complete wipe. dd /dev/zero.
The NuXT is based on the #micro8088 but with the IDE controller at a different port, so the NuXT has its own BIOS image, however the official NuXT image hasn't been updated for quite some time, but the Micro 8088 sees regular updates.
After even more faffing about with builds and tools, I finally had an up-to-date NuXT BIOS image with both V20 and universally compatible XT-IDE option ROM, what #Monotech calls a "hybrid" BIOS.
I have put it up on GitHub, it should be slightly easier to update it in the future. And there's a binary if somebody else needs it.