Glad to see that we're beyond the time when people would recommend old, standard-width (~8mm) chain for 6s freewheels.

When Shimano finally introduced their first narrow chain (UG-Narrow, a truly modern chain), a new standard had been set for best shifting on 5-8-speed freewheels and cassettes.
The earlier Sedisport was highly innovative as a bushingless narrow chain, but Shimano took what was learned there and spent years developing a better chain for their newer-style sprockets. Everyone else (among those who remained in business) then copied Shimano's work once the applicable patents had expired or a licensing agreement had been reached.

Sometimes even an 8s chain won't play nice with an older crankset's sprocket spacing, but it's worth it to do a bit of beveling to the smaller ring's teeth (or even bending the teeth a half-mm) to realize the shifting benefits of modern chain.