Exactly zero of those sites provide non-voip SMS numbers, which are what's required by Discord and the like. They can detect when a number is really VoIP-based and they block all of them.
There are plenty that provide non-voip numbers, but Discord will randomly challenge you later on if you do things like VPN heavily or block fingerprinting and if you can't access the number your account is toast.
I've verified with them successfully on Discord multiple times.