One of the best-written reviews I've ever seen here!
If you're looking for more Adastra, the writer began writing two new games: (Spoilers for those who haven't finished Adastra yet)
First you have Khemia: A sequel to Adastra happening 2.5 years after the Human's departure. In this game, you play as Scipio, a young wolf who's been chosen to go on a diplomatic mission alongside Amicus, Neferu, and some new characters (If you remember, there is a small scene at the end of Adastra in which Scipio tells Amicus the mission can begin). I'm guessing the story is going to focus on Neferu's relationship with his family, as well as on the political conflicts taking place on Khemia. And at last, I'm guessing the story is going to focus on Scipio x Neferu. "I'm guessing" because sadly, the writer suffered from a writer's block and is therefore incapable of working on the story right now. As a result of this block, the game is only 30 minutes long. Not more.
But! There's also another reason as to why the game's development is paused. And this reason is...
...Interea! Interea ("Meanwhile" in English) is a companion visual novel to Adastra, like some sort of spin-off, focusing of the Moon Tour's events (if you remember correctly, during Adastra, Amicus promises the Human he'll take him on a Moon Tour. Well, in the game, the events of this Tour are only summed up in a few lines. Vague descriptions of cities, etc...). Well here, the entire Interea game is about this Moon Tour. Be aware though that this game is still short and in development (maybe 1H long until you hit "To be continued...").
Hope I was able to help! :D
NB: If you want more EchoProject, they have two really big opuses: Adastra (and its universe, including Khemia and Interea) and Echo, a psychological horror Visual Novel, and if you love horror, I truly recommend it (and its universe, including The Smoke Room, Arches, Route 65, etc...)