rea987: You are right, it looks like HB nuked the Linux and Mac builds from users accounts that I am unsure how legal it is. Currently only Steam has the unadvertised native Linux build. I confirm that it's the default version on Linux.
https://steamdb.info/app/48000/depots/
Edit: This is quite weird. Limbo had multiple Linux ports back then, earliest Linux port was a cheap Wine wrapped port which wasn't performing well. Then another porter tasked to make a proper native port which is probably what Steam also offers.
I checked my HB library to see if other delisted Linux ports are still there. Dear Esther (standalone Source version) and Torchlight had HB exclusive Linux ports provided during few of HB sales of old. These builds can no longer be purchased, but it looks like they are still in the library of the users. So, Dear Esther and Torchlight's delisted Linux builds are still in users' libraries, but Limbo's native Linux build is on Steam as an unadvertised build, yet removed from HB users' libraries. Why?
Perhaps it was broken on current linux distros due to no maintenance, so they decided to remove it rather than having users complaining.