If the option dont work anymore either its a bug or steam has disable them options.
you are not allowed to prevent game devs update anymore.

ask steam support or try steam beta maybe, ( its not your game files its game devs )

other option do not have game installed you dont play, no more updates to them games.

When the devs of a game release an update Steam is required by the contract they have with the devs to push out the update to you.
The only choice you have is to not download the update and be unable to play.
Or download the update.
If you don't play the game anymore, uninstall it and you won't get updates for it anymore.

I understand that Steam won't let me play a game if an update exists and I haven't downloaded it.

However, I need to control when they're downloaded. I've had all my games set to 'update on launch' for years and it's always worked that way; going to Downloads would show a list of updates as 'Unscheduled' and I could start them appropriately.

Now I'm getting them as 'scheduled' even if they're set to 'update on launch'.

I just checked and it's doing this on all my systems, including my Steam Deck. I've opened a support request.

Could you resolve the issue?

Sometimes the Update system will try to schedule the update, but it won't actually update it as long as you keep it set to Update on Launch.

waw