Hi !
Google Keep : if you use google-chrome on UB and hit the google-boxed icon (small coloured squares - show apps) on bookmark bar, you will be presented a web page with large google app icons you use the most … if you Right-click on anyone of them and select “create shortcut” … you will end up with a wrapper on your desktop. I don’t use other browsers so I don’t know if it works elsewhere. Hope this helps.
Google Drive : I don’t use google drive much being scared of sync and what if your backup files get corrupted further to heavy on-line traffic. I prefer local storage with all the pros and cons implied. However I do admit google drive is super useful. The issue is syncing and network performance.
To my experience you can install KDE Connect on UB (and bloat it with KDE libraries). You may also find on google play store the same app for android smartphones too that must be installed. However I find that KDE Connect is not very stable 
so I dropped using it (unfortunately).
I was impressed by SWEECH app (see play store). Launch it on your smartphone and can browse from desktop through URL on relevant file system. Simply follow instructions and a file manager pops-up. (A must have for me)
I’m no developer myself, just an UB enthusiast.