I posted this message into Gemini Planet's Facebook group as well but it might be good idea to post it here as well:
"I'm 100% sure the automatic screen rotation used to work with my Cosmo with the stock FW version (V15) installed: After I ticked "Force landscape" and "Force portrait" modes off from App bar's settings the automatic screen rotation worked when I rotated the device. After I upgraded the FW to V19 it stopped working. The only way to rotate the screen is manually trigger it from the App bar: "Force Rotate".
And I just verified the automatic screen rotation is working with the same settings in my Gemini PDA. So I assume this is a bug in Cosmo's latest firmware(s)?
Luckily I was able to create a workaround by using Tasker to force the screen oriantation to landscape or to portrait mode, depending the state of "orientation sensor". Now the screen is rotating automatically if I rotate the device. But still I think this is a bug in Cosmo's Android. I've reported this issue to PlanetCom, let's see what they'll respond..."
And here are the screenshots how I implemented this in Tasker: https://imgur.com/a/MrcMDub
Cannot confirm, before updating from V15 today tried, and the only difference with the AppBar modes off was updater app launching in portrait, opera/chrome/firefox would not autorotate on v15 and v16, don't think this is a regression, just unlucky decision from start it seems