Why should they be forced to allow other retailers to sell Steam keys at whatever price they want

Because those other retailers already paid Steam for those keys.

If Steam doesn’t want to compete against third party key retailers then the solution is not to sell keys to third party retailers. Once Steam takes their money, they have to accept the competition.

They can. IIRC, Amazon apps would check to make sure the Amazon App Store was still installed. And I’m pretty sure Netflix games stop working when you unsubscribe from Netflix

Because the developers want to check whether you got the app from the Play Store.

If the developers don’t care where you get the app from, then they won’t check.

For one-off file transfers between any two devices, I like to use justbeamit.com

For a long term link, use syncthing

This is the easiest way. After installing the game, Heroic even has a command that will add it to Steam (with artwork IIRC).

My sort of interesting experience:

I tried to buy the LE on launch day, and couldn’t get through the payment page. When it was listed as sold out, I bought a regular deck without much difficulty.

Then I saw the LE was available again, and decided to try to buy it again. I was planning to cancel my original order if I could get the LE.

I tried to check out dozens of times over the next 24 hours, but on the final page I kept getting the “something went wrong” error.

About an hour ago, I decided to cancel my original order (you can do this by requesting a refund on the order page). The refund was issued 15 minutes later.

I went back and tried to order the LE again, 30 minutes after the refund was confirmed. Went through on the very first try.

So from my limited experience, I think Steam might be blocking all LE orders (and maybe even regular deck orders?) if you already have an active order.