I was a little surprised to have to scroll this far down to see BeOS come up. The first Amiga mention wasn't far above it either.

BeOS-lineage Binder IPC continues in Android.

I'm booting and running Haiku on my Thinkpad. It's a from-scratch workalike of BeOS, and able to run Be software. Though, frankly, Be software is totally 1990s, so a lot of Linux software written for Qt has been ported to Haiku.

In the end I wound up with basically the same application software as on my Debian desktop, except running on Haiku instead of Linux. Haiku is noticeably snappier and more responsive than Linux+X+Qt+KDE, though.