I've seen another post here, basically showing the same issue that I'm having recently.
I play Clash of Clans, and out-of-blue, my full-screen, landscape keyboard one day turned itself into a 'float'-ing keyboard, without allowing me to set it back to its original - landscape, full screen mode.
I have since then tried to clear the cache, re-install both Clash of Clans and Swiftkey, dig into the settings, restart the phone and pretty much do everything in my power and to my knowledge to try and troubleshoot the issue - nothing seems to have worked as the issue still persists.
What's strange is that it's only Clash of Clans where the issue persists, while the landscape, full screen mode work in any other app e.g.: Twitter, Google and so on - and it also has the options enabled to change it to my preferences.
Since I do not know about any work-around option, I just thought I'd post this here, perhaps other people having same issues could contribute saying which of the apps do not work properly for them - and maybe you could help the developers troubleshoot and fix it as soon as possible.
I have included a few screenshots with my issues.
Region: United Kingdom
Device: Google Pixel 2 XL (Android Oreo 8.1, 5 May Security Patch)
Clash of Clans version: 10.134.15
Swiftkey version: 184.108.40.206
PS: Changing the theme did not work and I have 3 language packs downloaded and used in QWERTY (English UK,US and Hungarian)
Thanks for the help.