Just upgraded to SteamOS 3.5.5, now that it’s on Stable. Unfortunately, it looks like Valve never addressed the issue if it not being able to mount microSD cards. I dunno how that got passed QA testing. I had this issue back on Preview, and assumed it was just a Preview issue, and went back to Stable.

Has anyone figure out how to get cards mounted again, or am I SOL until Valve fixes it?