Says who?

Just make a white-label (that is the key to making all this work) operating system whose maintenance you have full control over, and license it to other vendors for a small fee (not $120 or $200 per PC so you don’t put them off) or perhaps maybe even for free.

Then you will have a sort of Borg Collective of vendors all running their own OS’es, but on the inside you have the same tech stack (Linux???)