This isn't a guide, just something i think may help. To install Steam on an Arch-based distro in most of the cases a simple sudo pacman -S steam will do just fine.
The installation will ask you to select a valid vulkan package from a list. And in most of the cases that's just fine... most of them.
Then you have your very "picky" old nvidia GPU which works only with a specific old nvidia driver and if you try to install anything else, there will be a conflict. Now you can try to remove the old (working) drivers and try your luck. But looking online i find a simple way to skip this passage and install Steam.
sudo pacman -S steam --assume-installed lib32-vulkan-driver
I have to reinstall the driver for my ancient 1070Ti pretty much every update.
Interesting. My 1070ti works fine after every update. I switched to CachyOS after it lost mainstream support, so maybe it's that? Idk. Best of luck figuring that out, though, sounds awful.
Maybe dkms isn't automatically building?
And yeah, like Jo4 suggested... you should try Cachy. Support is way better than stock Arch because all that is preconfigured.