Draft: 2.15.0 release candidate
This includes my own !572 (merged) and !571 (merged), Ico's !554 (merged), !557 (merged), !563 (merged), and !568 (merged), and Guillem's !560 (merged). All fully merged, with merge conflicts fixed and with proper merge commits included.
These are all finished, have been tested very extensively, and are as ready as they'll ever be without getting them out in a release.
All that remains to be done is merge this MR to master, bump the version number and tag the release.