To add to what you have said:

Valve is an effective monopoly.

A lot of people seem to think 'monopoly' means 'literally 0 alternatives for the consumer', but this is not the case in either actual economic jargon/theory nor in basically any legal definition of it I am aware of.

To be a monopoly you basically just need to be the clear dominant actor in some market. Not the only one, just the main one, such that you can make pricing decisions in a way that other actors in the same market can't, basically.

Its... very rare for a 'true' or 'perfect' monopoly to ever exist for basically anything other than a public utility/service. It almost never happens.

This is the kind of pedantry that is annoying but unfortunately important, similar to how 'Impeachment' by the House on its own is actually pointless beyond a mark of shame unless it is also followed by a 'conviction' by the Senate.

You are correct that in US law, a major factor that is considered is whether or not the company did abusive, deceptive, underhanded stuff to achieve its monopopy status.

But UK law appears to be different:

https://www.lexology.com/library/detail.aspx?g=c5b1e681-5fb5-4161-bebf-823034fab751

You could be doing 'abuse of dominance' whether or not you achieved that dominance by underhanded means.

So... while I am not a lawyer, I would be genuinely surprised if Valve was found in serious violation of existing US monopoly laws, but I would be less surprised if they were found to be in violation of existing UK monopoly laws.

Yeah this is so stupid, just sounds like a baseless money grab.

That isn't necessarily true, companies with SMP have additional regulations. Steam having terms in their contracts preventing sale for cheaper elsewhere would be abuse of their SMP.

Also monopolies are cool now, just as Google.