You can install SteamOS on any machine, but AMD GPU are somewhat required if you're not up to major tinkering. Valve does not officially support NVIDIA gpus atm; they are working on it.
Also, "There are side effects to allowing third-party stores" - what is this bs???
Do I need to link to Steve Jobs presenting the iPhone saying iOS is based on MacOS? Have you use installed software on your Mac from outside the App Store?
I've heard this over and over and my follow-up question is never answered... What would change for those users? This is about ownership of your device, if you're OK with Apple's walled garden - that they apparently can change on any whims - nothing will be shoved down your throat.
Apple fights hard to not allow users to install from other sources on devices they own, so they can charge rent from developers, then complains when some apps that are too big for them to control are installed from the sole app store.
The solution is pretty simple, let people use the devices they own as they want; allow multiple app stores; allow people to download binaries and install on their devices.
When I was working as a team lead, I rejected any PR that was not in line with the rules. I stopped the review immediately I saw the rule breaking line(s).
One time, a manager asked me why I rejected a PR at the end of the sprint, before the demo, and I said, as you wrote above, that it's my responsibility and if he wants to overrule me, he should do that officially by assuming responsibility and escalating to our boss.
Make sure the rules are clear and then stop trying to appease.
edit: I wanted to make it clear that the rules were broken only when a new dev joined the team, after a rejection or two, PRs were extremely rare instantly rejected.