Valve Patches SteamOS To Fix Slow Wireless Speeds On Some Routers
Most recently, the SteamOS 3.8.22 Beta (as well as Stable version 3.8.14) have addressed an issue with Wi-Fi connectivity. This issue is related to Wireless routers that advertise incorrect MCS (Modulation Coding Scheme) speeds. MCS is intended to allow routers to offer improved capacity and device priority for MCS-enabled devices like the Steam Deck, but if the information reported by the routher is incorrect, it results in lower speeds. The latest SteamOS update reportedly fixes this issue on impacted devices.

It's unclear if the Steam Machine was included in this patch or not, but existing documentation for Steam Deck Beta and Preview channel updates also applies to other SteamOS devices. While Valve does seem to be updating SteamOS regularly, even adding Intel GPU support last month, it has a lot of work to do maintaining its OS across the existing pool of AMD/Intel handhelds and compatible AMD/Intel PCs.
Even with the desktop release now finalized, NVIDIA GPUs are not yet supported, which is obviously a let down for GeForce owners wanting to switch to mainline SteamOS instead of an alternative. There are also concerns around the Steam Machine's "Red Line of Death" error, though real-world reports of that remain limited and don't suggest any widespread defects.

Besides the SteamOS 3.8.22 Beta release with the Wi-Fi MCS fix, the 3.8.21 Beta also addressed numerous device-specific fixes.
The Steam OS 3.8.21 Beta update included fixing a delayed splash screen on the Steam Machine and a 20-30s startup delay on non-Valve devices. Specific device regressions were also fixed, including a Guide/Quick Access Menu button issue on MSI Claw handhelds, the gyro failing to initialize on the Lenovo Legion Go 1, and rumble not working on the OneXPlayer F1. The OneXPlayer F1 and OneXPlayer 2's special edition models were also previously missing controller support, which has since been fixed.