@Bloomfer @Tony @maegul @arinbasu1 That's a reducing issue these days as IPv6 becomes more prevalent as it is (with the UK providers I've worked with) effectively gives a fixed large range. You need to use Cloudflare or other CDM to proxy it for IPv4 users but that's free for small instances.
More to the point Mastodon is reportably difficult to install without a IPv4 connection. But that should be fixable by the developers. Hopefully soon.