As I'm a former Recalbox dev, I can tell you :
- you can get ES, it's already halfway done, so to say
- I have written a AM to ES systems converter
- Don't expect all the features in ES that are specific to Recalbox
- I have anyway set my mind on the retrobat/batocera ES which is more "portable" than the Recalbox', which is anyway way too linked to the distro itself
But I haven't done much on ES for, say, a year or so