Yes, but if someone created a "LinuxBox" emulator that provided a stable, never changing, fixed target for Linux software, I would be happy to have that install

Yes, but if someone created a "LinuxBox" emulator that provided a stable, never changing, fixed target for Linux software, I would be happy to have that installed everywhere and use it the same way I use DOSBox now. That would be possible even if Linux itself keeps evolving and diverging away from whatever version is emulated in that LinuxBox. But it would require a dedicated community of some critical mass that could agree on the importance of never falling to the temptation of ever upgrading any APIs bundled in that LinuxBox.