I’m guessing the OP meant “where glibc is really horrible”, since bsd libc is rather more abi stable, largely because that’s where FreeBSD provides compatibility instead of the syscall layer. This is not to say you can’t use an old libc and fix up the loader paths or use a container and make it work, but it’s a different set of challenges.

> bsd libc is rather more abi stable

I am not sure about other BSDs, but at least OpenBSDs is all but abi-stable; when they wanted to introduce 64-bit time_t to fix Y2038, they just changed the typedef and declared a flag day.

I had trouble trying to run libc5 era software a few years ago. This wasn't the kernel but the distro did not make it easy. I wouldn't expect them to keep maintaining libc5 packages 20+ years later either.

I think if you do anything GUI-ish over the last 20 years there's been many shared library breaking changes. But that'd be true of FreeBSD too since those dependencies are just the same when they live in ports.