Not every knows about the DNS settings and some Nigerians might need it with the way things are moving.... If you have any good resources you can drop it.
Are you sure is a dns level ban?
As for changing it, it can't be any simpler than this, at least for Android as that's what most use, just go to settings, type DNS and you get the Private DNS settings, and you change it from automatic or off to custom as you add to Private DNS provider or DNS provider Hostname for example "dns.google" as I doubt the Nigerian authorities have enough power to force google to enter customs bans.
But as I said before, if this doesn't work using VPN might be risky, you don't know when exchanges will use that as an excuse to steal your coins, just because they let you do it for a while it doesn't mean they won't selectively pray on a few.
Over here in Greece there's also a very expansive list of online casinos being blocked, which includes most crypto casinos too. But it can be bypassed by simply changing the DNS on your computer. So I would assume most crypto users are already educated enough in computers to know how to bypass these silly blocks.
Same here somewhere back in 2016 or 2018 can't remember, but in my case the moment I managed to access my favorite betting website I got one huge announcement about how they wouldn't support customers in my country anymore and to withdraw my balance as soon as possible as my account would be frozen until the site will get a license for operating here!
