Delta Chat is using Mapbox tile server to show the map if you enable experimental “location streaming” feature and open the map. It is not used as long as you do not enable this feature or use it only to send your location but never look at the map.
Delta Chat for Android also opts out of Mapbox telemetry, so the tracker is not actually running: init mapbox only as needed and disable mapbox-telemetry by r10s · Pull Request #886 · deltachat/deltachat-android · GitHub However, the tiles will be downloaded from Mapbox’s AWS servers, so Mapbox will be able to collect some statistics about which parts of the map you download, and associate it to your IP address, but not your email account.
Switching to offline maps would be nice, but is low priority currently, as “Location streaming” is not a primary feature of Delta Chat:
If you are concerned about possible tracking by Mapbox, don’t enable “Location streaming”.
Overall this tracker detection is a “false positive”, Exodus does not analyze the code but warns about any inclusion of Mapbox SDK in applications. You can also see a discussion in F-Droid repo, users run Exodus from time to time and report this to F-Droid maintainers: Delta Chat now contacting third party servers (map provider) for position related data (map tiles) (#1611) · Issues · F-Droid / Data · GitLab