How do I find out if any altnets are serving that area?

Recently, I've found out an altnet is approaching my area. I've found that a different altnet is also in the different area next to us.

For example, Grain Connect is in Manchester, so is Brsk - they're next to each other in some areas. I would have never known those altnets existed hadn't I discussed with people who live in there as they advertise by putting out leaflets.

I'm moving out soon, so I want to find out about existence of altnets when searching for properties.

How do I do that if I don't know which altnets might be serving that property?

https://bidb.uk/ is pretty good for this, and includes mobile data coverage too.