Although Breakthrough Photography announced their filters for the Canon EF to RF drop-in filter adapter first, they weren’t the first to bring them to market. The filters themselves should start shipping this month if they haven’t already, but they’ve also expanded their offering with an EF to RF drop-in filter adapter of their own.
They claim it’s just as capable as the Canon original, with full electronic contacts for autofocus and image stabilisation, as well as transferring the EXIF data. It’s compatible with both the original Canon drop-in filters as well as Breakthrough’s own (and presumably Kolari’s). Except, it’s $100 cheaper than the Canon one.