Currently there's ongoing heavy development before next v1.27.5 release, so I'm low on resources, as most of them are currently used for testing various aspect of new release. There's a mirror net running but at this moment I think there's no corresponding full haf node for that, but basic API (get_block, network_broadcast) should be available at:
http://seed.fake.openhive.network:8091
(that's mirror net so chain-id 42)
I don't plan to run old-style testnet (other than mirrornet) as it is something that people can easily run in their local development environments (very little resources needed)
Please let me know what do you need exactly and I'll try to help