Not sure it checks all the boxes but perhaps GrapesJS?

I’ve got 6 radios running it! A couple use mqtt to push the messages off the mesh and onto the cloud where it’s a little more convenient to receive messages.

Overall I am using it to set up a little emergency comms for friends and family, but I hope to use it hiking/biking/backpacking as well.

Super active community on discord, and they have a subset of users on matrix as well.

I’m currently working on this, using git and having GitHub actions produce artifacts when building the markdown files to pdf. It’s great!