Depending on what region you're in, the Lenovo Legion Go 2 might have already landed and it seems like SteamOS might come officially in future.
For the original Lenovo Legion Go and the new Legion Go 2, the only officially supported operating system is Windows 11. However, Lenovo did launch the Legion Go S with a SteamOS version officially supported but they've stayed pretty quiet about SteamOS for the Legion Go 2. The only note about it I've seen previously to now was a minor mention at the bottom of an article on The Verge where they were told simply "Lenovo isn’t announcing a SteamOS version of the Legion Go 2 at this time".
Lenovo recently did an AMA (Ask me anything) on Reddit, where the Lenovo Legion team were answering questions. And, of course, someone had to ask about SteamOS. From the Reddit post by a Lenovo official:
While the Legion Go Gen 2 is optimized for Windows to deliver broad compatibility and a full gaming experience out of the box, its open hardware platform allows for users to explore alternative configurations if they choose. We are exploring official support for SteamOS on the Legion Go Gen 2.
While usually you could mostly ignore such a comment, and put it down to the usual non-committal marketing speak, the fact that Lenovo have done a SteamOS machine before adds a bit more credit to it. They could have just continued to say no like they did to The Verge.
Hopefully they won't leave it too long if they plan to do it. Otherwise, you'll have to wait for Bazzite to continue improving support for it to get Linux on it yourself.
The Legion Go 2 starts at £1,099.99.