You should use the latest Testnet version for sure, which is v4.  It isn't "broken".  A few people are just testing in ways that disturbs others, but that is the point of Testnet.  The mining should change with a fork Jan 2026.  Then it'll just be flat out mining, similar to Bitcoin, and should be best IMO.

Anyone leaving the default as v3 is just being lazy.  Core will drop v3 and services should be long since upgraded... or it could / will be a bit of a cluster fuck (but good for learning.). You should definitely ask services/maintainers to please upgrade... There are a lot of people who don't even know Testnet v4 is out.

Upgrade and prepare your project for Mainnet.  The latest Testnet should be the closest to Bitcoin.

Also, if you want something in this space and it doesn't exist... build it.  Others may need it too, and it could be a business.

You should use the latest Testnet version for sure, which is v4.

Anyone leaving the default as v3 is just being lazy.

Upgrade and prepare your project for Mainnet.  The latest Testnet should be the closest to Bitcoin.

Also, if you want something in this space and it doesn't exist... build it.  Others may need it too, and it could be a business.