My bad, I thought I was creating this issue in https://github.com/ValveSoftware/steam-for-linux/
Is it possible to move it ?
Yes, every time there is 5mb localization update for dota 2 steam downloads 500mb shader cache. Isn't the shader cache supposed to be calculated client side? Also why would every update invalidate the complete shader cache?
E: I have disabled shader pre caching for now, vulcan doesn't work for dota anyway ( https://github.com/ValveSoftware/Dota-2-Vulkan/issues/382 ). Why is there no per game setting for shader caches? No point downloading vulcan caches for a game that isn't going to use it.
Nothing extracted yet.
Your system information
Steam client version (build number or date): Jun 8 2021
Distribution (e.g. Ubuntu): Ubuntu 21.04
Opted into Steam client beta?: No
Have you checked for system updates?: Yes
What happens
Step 1

Launch Dota2, check "Launch game as soon as it's ready"
Steam client downloads Dota2 shaders
Small inconsistency : "Ready to launch" is shown
Step 2

Launch fails with the pop up below
In the background, Steam client downloads a game update.
Wait the game update to finish.
Press OK to dismiss the pop up.
Step 3
Launch Dota2.
A pop up shows "vulkan processing", then the game starts
Note : it's not game specific at all, I just reproduced this with Tekken 7.
What should happen
Launch Dota2, check "Launch game as soon as it's ready"
All updates are handled automatically, then the game starts without further user interaction.