This may be a "won't fix" because it only affects the gen2 CameraMappers, but lsst, subaru, decam, and cfht all use filter.getId() in their calculation of the singleFilter coadd exposure id. The new FilterLabel does not have a numeric Id, so these mappers will have to be changed. However, I do not know what the time ordering of gen2 removal vs. Filter removal is: if gen2 is removed first, then this won't matter at all.
I did not change this on
DM-27170 because I did not want to alter this calculation in gen2 without more discussion, and want to get that ticket finished up.