This RFC proposes to deprecate obs_sdss and the lsst_stack_demo. The stack demo processes a few SDSS frames and checks that the measurement results are identical to a saved set of measurements. obs_sdss is necessary to support the demo, and the most recent substantial usage outside the demo was in the Stripe 82 processing during 2013. The catalogs from the Stripe 82 reprocessing are still in use as one of the databases available in the science platform, which doesn't require obs_sdss, but the images are also served by the SODA service which does use obs_subaru.
Deprecating obs_sdss at this point would save the effort required to port it to Gen3. The demo also requires occasional effort by developers when merging measurement changes to update the fixed values it uses for validating the results. This testing is largely superseded by validate_drp, ap_verify, ci_hsc, and the squash framework for monitoring regressions. The demo does sometimes identify changes that unexpectedly modify measurements results (since it requires nearly bitwise-identical results), but this functionality could be added to either of the other CI packages. If this type of validation is desired, it would be substantially better to add it to ci_hsc where it can monitor more stages of the pipelines, beyond single frame measurement.
Deprecating obs_sdss will require migrating the SODA service to use HSC data. This migration should be easier than bringing obs_sdss and the Stripe 82 repo up to Gen3, and serving HSC images is a worthwhile goal on its own.
As I understand the deprecation policy, if accepted, we should announce the impending deprecation in this upcoming 19.0 release and remove the packages from lsst_distrib after the release and once the SODA service has been migrated to HSC data. This RFC will need approval by the DMCCB.