There are no compatibility issues with friction... just when you mix and match earlier generation indexed parts and when you try to get modern Shimano, SRAM, and Campy to play together in indexed modes.

With travel adjusters and alternate cable routing you can sometimes get these differently spec's components to play together and every once in a while they will do it on their own.

The later generation Suntour indexed shifters often has settings for regular and ultra (narrow) spaced freewheels and these can often work well with modern narrow cassettes.