I'm not a Rails developer myself, but definitely noticed a lot of demand for Rails work in the various remote job newsletters I'm subscribed to. Can't say how much is legacy vs greenfield or whether this is a reflection of demand for a niche skill or that Rails is still a popular choice for companies. Either way, makes me regret a little I didn't stick to Rails development years ago as it seems quite lucrative even today.
It can be difficult to recruit for now.
(Also no, I'm not in web development, I have just observed this)