❔ Who can help?
"... as a first step, we should find a way to determine the location and hosting provider of all instances. This would help immensely in making an own judgement about the "greenness" of an instance. Unfortunately, API-access to geolocation and ASN information is usually only commercially available."
not true. By example, the list of ASN per country can be downloaded for free: of course then you need a software to process the database. The european ones, by example, are here:
you can just wget them like:
wget ftp://ftp.apnic.net/pub/apnic/whois/apnic.db.inetnum.gz wget ftp://ftp.apnic.net/pub/apnic/whois/apnic.db.inet6num.gz
wget ftp://ftp.ripe.net/ripe/dbase/split/ripe.db.inetnum.gz wget ftp://ftp.ripe.net/ripe/dbase/split/ripe.db.inet6num.gz
this covers the whole planet.
Once you have the database you need to paese it. There are already tools for that, like:
chaos.social – a Fediverse instance for & by the Chaos community