I don't think this is as much of an issue as you are making it out to be. I have my Steam Deck on the main branch release which seems to exclude it from downloading precompiled shaders. When a game updates it has to compile the shaders first, but even on a big game this does not take an unreasonable amount of time. Less time than it takes for game updates to download at least.

Steam could improve the experience here by having the shaders compile overnight in the background so it presents zero delay but the current way doesn't bother me much at all.

I remember Star Wars Jedi Survivor had a 5-6 minute shader pre-compile on my 5950X. I heard of people well into the 30 minute mark on lower core count machines. Battlefield 6 was a few minutes on my 9950X, higher again on lower core count CPUs.

Really depends on the game.

There's no easy way around this problem. It never came up as much in the OpenGL/D3D11 era because we didn't make as many shaders back then. Shader graphs and letting artists author shaders really opened pandoras box on this problem, but OpenGL was already on its way out by the time these techniques were proliferating so Vulkan gets lumped in as the cause.

You're getting lucky with the games you're playing, then; there are absolutely PC games that have had 20-30 minute long shader compilation times _on high-end gaming hardware_. (I think some of Sony's ports were known for this; Googling tells me Borderlands 4, Stalker 2, and Starfield also had notably long shader times.) Typically those occur within the game's UI after launch but before the game starts playing, though, which makes me wonder if Valve might still be caching a non-GPU-specific intermediate of the DX12 to Vulkan conversion, and _that's_ what Linux Steam clients are compiling pre-launch and/or sharing with other clients. That's pure speculation on my part though, as I haven't played any of the worst-case-scenario games on my Deck, nor have I done anything that would cause the shader downloading to not operate.