I thought TypeProf is really interesting but doesn't seems to get much attention.
I am also wondering if anyone is using RBS in production. Apart from big shops like Stripe / Shopify.
I believe Stripe and Shopify only use RBI in production since Stripe develops Sorbet [0] and Shopify develops Tapioca [1]. Both tools work exclusively with RBI files instead of RBS files afaik. I haven't heard of anyone using RBS in production.
[0] - https://sorbet.org/