![](https://lemmy.world/pictrs/image/d060ac2a-db78-45c4-8ac9-8b7e6d62949f.jpeg)
![](https://lemmy.world/pictrs/image/4271bdc6-5114-4749-a5a9-afbc82a99c78.png)
Flatpak steam can do all that. You just have to learn to control the flatpak sandbox. There are CLI commands of course or you can install Flatseal which is a real nice gui that lets you control the sandbox for each individual flatpak app. https://flathub.org/apps/com.github.tchx84.Flatseal
Just add whatever drive/directory/mount point in the filesystem path for Steam in flatseal and Steam can see it.
Not if you install Firefox from Flatpak. ᕕ( ᐛ )ᕗ