Is there another way to install apps on an older version?

I have an iPhone 6s but not on the latest version (because that slows down the phone) and I wanted to ask if there's a way to install apps in my version (because of Netflix and Steam link for the phone) I already know the one method If you have the app before you can install it in the older version, but I have not had these apps before.

It's just idiotic not to update it to the latest version. And slower it is not really strong