As noted at https://gitlab.gnome.org/GNOME/Initiatives/-/issues/17, all GNOME core components will use Tracker 3 in the next release apart from Photos.
There are also a few non-core components which still depend on Tracker 2: Games, Books and Documents.
Tracker 2 and 3 can be parallel installed. We recommend distributors create new
tracker3-miners packages for the new version of Tracker.
tracker-miner-fs-3.service (or /etc/xdg/autostart/tracker-miner-fs-3.desktop) should start with the user session
GTK+ should be configured with -Dtracker3=true
The latest release of tracker2-miners adds a
-Dautostart build option. It defaults to false. This means that tracker-store.service and tracker-miner-fs.service will not autostart with the desktop session, and will only activate when an app requires them.
I also sent this as a mail to email@example.com (although it may be stuck in the moderation queue)