So just an update on this…
Still looking into it but it seems like existing Groovy integrations will not stop working at the end of 9/22. They will only disable creating new ones. Might be wrong here but that’s how I took it. Source
Obviously this is not a long term solution but it does seem to buy some time here. It does look like the whole ST edge thing is completely different and will require significant server-side changes. This is a little difficult since this is not just a SmartThings exclusive project anymore. The project is also 5 years old now so maybe it’s time for some changes on the server anyways 
Feel free to like this post to kinda help gauge interest in this. This might be a decent amount of work and I’ve been off of SmartThings for a little while now so it would be nice to see how much interest there really is. Always up for a challenge though. I’ll keep this updated with any progress.