If they don’t keep any private data on any computer that trusts their home network/wifi and don’t do taxes or banking on those, there’s no problem.
But if they do, I maintain that the analogy is correct: their unpatched machine is an easy way to digitally get access to their home, just like an unlocked door is to a physical home.
Steam Deck and Linux desktop user here.
I wouldn’t prioritize a native Linux binary if I were you. For some of my games that have a native Linux version, I still run the Proton compatibility version instead because it runs better. Proton is insanely well-optimized and adapted to Linux desktops, your own code will have a hard time competing with that.
Just make sure to pick an engine / tech stack that works well with Proton and find one or more testers who run SteamOS or another Linux distribution.