20GB of OS is quite normal for a modern desktop. Steam Deck actually has two copies of the core OS installed, to ensure there’s always a bootable version and to make upgrades painless. A basic Ubuntu install requires 8.5GB of storage and that doesn’t include Steam or Proton.

Compare this to Xbox, where the 512GB drive has 148GB of system files and reserved space. The 32GB Switch reserves about 6GB and the Switch OS is purpose-built rather than a Linux distro with Steam bolted onto it.

It sucks that consoles are advertised with their storage size rather than their usable storage size. They should really put the usable storage on the box rather than the theoretical size, especially when they sell different storage tiers.