Just got my I3S 45mm. Following might be of good info to someone, as I couldn't find much online:
The glass circumference of the Instinct 3 Solar 45mm measures at 34mm. I have a 32mm screen protector installed, which is the right size for an Instinct 1, which I had around. Photos also show both watches side by side.
The I3S glass seems to be dead flat and not slightly curved, as the tempered glass screen protector (32mm meant for the original Instinct) self adhered immediately when dropped, so I believe you could use a generic tempered glass one at 34mm.
No issues or interference with the solar panel with the protector on. Put the watch by the window under the sun and it started registering max solar intensity right away.
The watch updated to the newest firmware, 6.29 through Garmin connect, wirelessly, without the need of a PC through Garmin Express. It came with the 5.19 software, that showed the reported bugs, such as the much lower battery expectancy, and no lux hrs registered.
more info: It does properly display Mandarin, and possibly (not tested) other Asian characters / font (I3S purchased in Canada)
