I was looking at anarchy servers a while back for my son to join, since he wanted to play with other people but he also loves destroying absolutely everything. Thought it'd be a good fit.
Couldn't really find anything though. Most were complete bedrock wastelands at spawn and there was no escape. 😕
Sounds like Minecraft PE/BE, there are no server sided checks on inventory in the pocket/bedrock editions of Minecraft so people can effectively generate any item they want.
That issue doesn't exist in Minecraft Java Edition and to my knowledge doesn't exist in Minetest either, they both make sure that players only have items they've received.
I wouldn't really consider anarchy servers suitable for anyone under about 14-15 years old, given their nature they often bring out the worst in people.
As for spawns being wastelands, that's very common, though they shouldn't be made of bedrock. Minecraft's oldest anarchy server, 2b2t, has spawn wasteland that's roughly 10km² and it's such a challenge to escape that there's actually an official speedrun leaderboard for escaping it.
If your son is younger than about 14, I'd recommend running your own server. It might be a bit daunting at first but really isn't all that difficult once you have everything up and running.
I know all about how to make a server, haha, used to host one 10 years ago. Not daunting at all. I just personally didn't want to host an anarchy server, hence my desire to find someone else's. 2b2t was the first one I actually looked at, and yeah, definitelyyyyy a massive spawn wasteland.