There is a launch argument you can add in steam, '--skip-launcher' for bg3. You won't be able to change between the dx or vulkan clients though without the launcher, if that matters to you (probably not, but figured I'd mention it). I'd guess there is a similar option for Cyberpunk 2077, but haven't done it personally.
Don't know how to do it from Steam, but you can just launch their main game exes. On Linux you could add the exe to Steam or just use Wine or your Wine frontend of choice.