Bumping this a bit after doing some more research.
I had noticed some discrepancies between my RP's coordinates via the iPhone app and other camera's results shooting at the same place. Not sure why.
For that and some other reasons looked in GPS units, and was considering the Solmeta. But then I blundered into a used GP-E2 at my local camera store for cheap. So I took a chance and bought it.
Bottom line, glad I didn't pay much for it, and I'd bet the Solmeta is WAY better.
The GP-E2 is ancient. Takes quite a while to acquire. I upgraded the firmware, which I though might not have worked, and it does work on my RP, but no heading info as others have noted. It's not terribly accurate either, which is probably down to an ancient GPS inside. And having a dongle that requires a computer to download tracks is pretty 2002.... If the Canon software goes away, that won't even be possible in the future, as it doesn't just mount so you can copy the log off.
What do you mean by the dongle, the micro-USB cable?
But hey, it works on the camera reasonably well. Won't show compass direction though.
All in all, if one doesn't get lucky and find a used one I'd go with another solution.
I don't have the R5/R6 but I have the R. Coming from the 6D (follow up of the 5D/5D2), I also missed having the onboard GPS on the R series. However, I had the GP-E2 since 2016 and it has worked well as the standalone logger and hotshoe GPS tagger.
I was not aware that the GPS on the GP-E2 was ancient and slow but I thought it was slow acquiring signal because it was not always on like the GPS on smart phones. Now that you said that, I will be paying attention to the Solmeta units or alike in the future.
I have been using the GP-E2 since 2016 as a GPS logger to tag photos taken by my Canon and non-Canon cameras without the onboard GPS, such as the Sony A7III, Panasonic FZ1000, Canon M3/M5, Canon G5X and the R. It has been working great to record GPS locations for places that I traveled around the world.
I also purchased the GPS Photos app for my phone as a backup GPS logger.
I left the GP-E2 in a church at Sweden in 2019 and had to buy it again. Luckily, I found a used one on Amazon for less than the full price. The used GP-E2 can still be found on Amazon for about the same price.
Canon have removed some features from the GP-E2 software. The GPS log generated by the GP-E2 is not in a standard format and may have to be converted to be usable. However, I found the good and old Downloader Pro can read the GP-E2 log files and tag the image files on the fly while downloading. If the GP-E2 is attached to the R/R5/R6, the image files are tagged automatically. So the GP-E has been a reliable part of my workflow.