I've only worked at (several) places not on that list, but I will say that despite everyone's snide remarks here about how nobody uses Haskell..I have been able to immediately get multiple Haskell interviews whenever I've wanted. Ping some recruiters & former coworkers on LinkedIn and it's done. Niche languages have their advantages. And despite "there only being dozens of us," there's plenty of money in Haskell out there to make a good living (no passion paycuts). Gotta know Haskell first tho ;)
What about reforming existing engineers? Especially ones that have gone down the operations path for several years and want to get back to contributing with code?
Edit: I was asking kind of flippantly, but actually upon reading your team and product seems quite interesting. Would you be up for a chat?