sounds just a tad paranoid.

Yeah, I would say that some years ago. Now it’s just waiting for more of the same to happen.

the android situation is not really comparable to desktop linux.

google has a monopoly over the distribution of all apps, android has never really been independent of the playstore.

Doesn’t mean it has to stay that way. In Poland we had a telecom monopolist that was never anything else than a phone company. Yet, we split it into infrastructure provider and service provider. Miraculously internet got faster.

unlike desktop linux which has an established ecosystem already

Google took that open ecosystem and built a walled garden out of it. That’s what Valve is doing.

they can lockdown their steamdeck & steamos but there is no point in running steamos unless it comes preinstalled.

Steam OS is so good people install it on Steam Deck competitors. In time it will be preinstalled there too. This amount flexibility would suit Valve and is exactly what happened with Android. Remember people installing it on HTC HD2 and such back in the day?

and they cant really make the installation on other distros more "fidly", because the package manager handles installing software.

Once they’re at the point described above it becomes very easy to introduce minor annoyances that push you towards their services.