I finally got round to testing it out, and can’t say am all that impressed.
The main problem is that I couldn’t find a cpl for the ultra, meaning dashboard reflections were a problem. Image quality was also lower than a gopro attached to the same windshield, with quite a lot of wash out.
Disappointingly, garmin seems to be still finding camera software hard (probably because of really old hardware), and white balance/contrast is very erratic and adjusts with a delay (it’s the virb x/xe issues all over again!).
I wanted to use 1fps shooting, but ended up going to 2s as the battery was dying too quickly and there is NO way to securely mount a virb ultra while charging out of the box - the waterproof case is sealed up, and you need their proprietary cage case. With garmin tax, obviously.
The battery in this mode lasted for ~1.5 hours before giving up.
Also disappointed with gps performance (for a device with so many sensors!), as it was drifting after a cold start fix, and generally takes a bit of time to get a fix.
Not sure if needed for mapillary, but the ultra doesn’t write image heading into exif, only track direction - fixable with geosetter, but takes time
Happy I didn’t pay full price for it