Non-existent to a close approximation (maybe more Elixir stuff out there than the others you listed but still very rare). Learn those languages if you’re interested and curious but if the goal is to get a job with a new to you language, stay as far away as possible from them. Not only are there very few jobs but also the niche languages will distract you from learning stuff that’s in demand.
The total amount of supply doesn't matter much. What matters (both for the employer and the job-seeker) is the ratio of supply to demand.
E.g., let's say JavaScript has the most demand of any language and there are 2 zillion job openings. This sounds great for job seekers initially, but what if there are 5 zillion JS devs seeking jobs? In that case job hunting might be very difficult. Similarly if there are 100 remote positions open in Pony, but only 10 Pony devs available to fill them, job hunting might not be so difficult.
There are some liquidity advantages in absolute scale, but for the most part it's the ratio of supply to demand that matters and not the raw numbers.