It seems more Linux ports from Feral Interactive are no longer advertised on Steam, with the latest being Tomb Raider (2013).
This follows on from the same happening with Mad Max and Shadow of Mordor in Early 2021. Much the same, the Linux version is no longer advertised but it is still available to install. Later that year in April 2021, Feral did bring out Total War: ROME REMASTERED but then we also saw that Feral confirmed in July 2021, that they would no longer be porting A Total War Saga: TROY to Linux - citing "generally less demand for native titles since Valve’s launch of Proton".
Given how far things have come, the original Tomb Raider OpenGL port wasn't a particularly good show for Linux gaming. Compared with later ports that used Vulkan, it did not perform well. Seems like the port was in a rough state overall now too, checking back on it today and it wouldn't run unless forced to use the Steam Linux Runtime container and in-game there were lots of graphical problems on NVIDIA.
Currently, Feral are working on the Linux port of Total War: WARHAMMER III, which is due out for Windows on February 17 with Linux (and macOS) "in Early Spring" according to the Steam store page.
We have reached out to Feral for comments, will update if they reply.
Update - 15/02/22: Feral press replied to say "The Linux version of Tomb Raider (2013) has been removed from sale due to the license expiring for that specific title. Rise of the Tomb Raider and Shadow of the Tomb Raider are still available to purchase on Linux.".