if you like Tailscale, you should look into Netbird.io! It’s the same concept but 100% Open Source
They have a feature called remote SSH access where the agent running on the node allows other VPN users to SSH to another machine on the network without having SSH enabled / public keys set up. I've tested the project at the beginning of the year and it was a big NO for me. They seemed to fix this issue but it appeared again.