Canon is moving on from the EF-mount lenses and SLR cameras which (including film) I have been using since 1999. All the new stuff is RF mount for their mirrorless cameras. I took the plunge recently with the R5 Mark II camera and two RF lenses, the 100mm macro zoom and 14-35mm wide angle zoom. Since I still have the EF-mount 6D Mark II as a backup, the plan is to keep the four EF lenses I still have (24-105, 70-200, 100-400, 500) and use the EF-RF adapter when necessary.
The R5 and 6D take the same battery.* That is a big asterisk. The batteries have the same form factor and use the same charger, but are NOT the same. The battery from the 6D will power the R5 to take still images, but the faster burst speeds and higher video resolutions are not available. Oh well, I don't shoot much video anyway. But there is a possibility of Aurora Borealis tonight, so I plugged in the AC adapter that I was using with the 6D and the dearly departed 5D Mark III. It doesn't work with the R5.
Canon's official solution is an adapter that plugs into the camera's USB-C port. The Canon USA site does not say whether the device will power the camera, or just charge the battery. I don't need a $150 battery charger, I need a power adapter. I tried watching a You-Tube video that supposedly demonstrated the device, but the guy was so disorganized that I gave up on it. Just a suggestion for You-Tubers, minimize your fumbling around by taking a minute to jot down a script outline, and learn how to use the basic functions of DaVinci Resolve to do some simple edits of your video before you waste everyone's time with a disorganized mess. Additional searching found the Q&A on the B&H site, which is probably as authoritative as I will find given Canon's negligence, and it seems the device will power the camera.
On a more positive note, R5 has the same remote trigger plug as the 6D (and 5D). So, if I wanted to, I could use either the motion trigger or the remote trigger. The upside of using the R5 instead of the 6D is I might be able to get away without prefocusing, and instead let the new camera's eye recognition set the focus. It supposedly works with animals. I tried a few autofocus sessions at the birdbath last summer, and the success rate was very low.
Anyway, one of my new lenses is a 14-35mm wide angle zoom, and I want to use it tonight in case the predicted Aurora is visible. I will use the built-in intervalometer set on unlimited, start it at about 9:00, and see how long it lasts before the battery dies. Here's a stitched panaroma of Red Lodge, MT that I shot just after I took delivery today. Below that is a followup to the previous post, another shot of a turkey with the 100-400mm zoom with the RF-EF adapter on the R5.