Hello,
I can see that the ODK XLSX specification and PyXForm still support OSM (See example here: https://docs.google.com/spreadsheets/d/1X1piJFPjgFo6sr2uTXtghFvtfdi7RRiWkNzWloILhzM/edit?usp=sharing) however OpenMapKit hasn't been updated and it does not work in the latest Android.
Is this something that we should consider as legacy / deprecated or is still part of the ODK Ecosystem?
Red Cross stopped actively maintaining OMK several years ago. For some time, HOT OSM was maintaining a fork of OpenMapKitServer but I don't think they ever worked on the Android app. The changes to file storage in Android 11 broke how OMK worked with Collect. I think you can consider it legacy. It is hoped that the planned work on the roadmap for longitudinal data collection will eventually encompass geospatial feature/ OSM workflows.