Got a Steam Deck (ostensibly for the kids, but they only get to use it docked). Overall, I am thrilled with it - far and away the best portable platform I’ve ever seen. The downside is that I thought I had left behind “debugging Linux display configuration issues” like 15 years ago, and this is very much (like 100%) that same feel: trawling through forum threads and Reddit posts and a depressing lack of official documentation, while tweaking beta settings and doing updates and trying to figure out which of at least 4-5 sets of config options need to be modified.
To be fair - that's less on the steam deck and more on PC gaming forever having the hardware platform shift under it's feet; the situation you describe isn't "steam deck" - it's "pc gaming". You're old enough (I think?) to have had to struggle with IRQ settings and sound cards and needing to find the magic combination that worked...
Let me ask you this - are you seeing this problem with deck-verified games? The only difference here between this and, say, the switch is you're being allowed outside of the curated section into the jungle.
@Biggles haven’t even gotten a game launched - if I’m in game mode and plug into the dock, native screen goes black, and external display recognizes a signal input but also displays black. Issue apparently either EDID or HDCP. ¯\_(ツ)_/¯ I will test with an Apple USB-C to HDMI adapter later.
Very surprising; I'd be expecting valve to test their updates vs their own hardware prior to release. Are you running the alpha or beta release?
@Biggles nope. Bog standard.