Keep in mind that they did originally pick Debian. SteamOS 1 & 2 were Debian based (used for their ill-fated Steam Machine and Steam Link products), then switched to Arch-based for SteamOS 3
I will not accept ill talk of the Steam Link slander /s
I got mine for 6€ new when they stopped production. Don't use it much, but its nice to have that when I have a system no where close to an actual TV.