Alternatively, you could use Liquid Network. While the network is controlled by federation board, it utilize Bitcoin/Bitcoin network which partially meet OP criteria.
I never used Liquid, but I've read a bit about it. I don't really know if using Liquid would be open enough. I like the Idea of Lightning Channels.
Seems more like something everyone can use & setup without asking for permission.
I agree Liquid isn't open or permissionless enough, i never used Liquid either. Alternatively, you could check Rootstock (
https://www.rsk.co/) which have smart contract capability. It's less promoted than Liquid, but AFAIK it's more open and use merged mining on Bitcoin network.