The wait over here is for an l-plate. Lloyd Chambers (
www.diglloyd.com) fully endorses the 2-piece RRS BD850-L (even before he had a camera available to test it, go figure). However it requires the left strap triangle-shaped wire with plastic insert to be removed, making it a useless pita for people like me who do remove the plate on longer missions without a tripod.
Apparently RRS has listened to the many complaints about this, and has announced a single piece D850 l-plate called BD850-UL that doesn't require the strap to be removed. Much better and on order.
As expected, the Foolography BT dongle with D800 modification fits well into the 10-pin connector; together with a BT GPS mouse a GPS tagging solution that actually works, something that cannot be said about SnapBridge. Nikon BTW needs to be pressed to implement direct BT support for BT GPS mice.
I bought a Bad Elf GPS Pro+ GPS mouse; it allows to be simultaneously connected to more than one camera. it also has a GPS tracking mode making it possible to merge GPS data to files of my (GPS-less) Fuji's after ingesting. It also has the possibility to remotely trigger the Nikon through the BT connection, also a handy feature.