I use Gboard, as I'm on Android.

Do you use Gboard or the clipboard feature? Or use a similar feature of an other keyboard app?
Do you use apps like NetGuard or TrackerControl to restrict net access to the keyboard apps?

Have tried some FOSS apps some years ago, but didn't stay on them because, Malayalam(my mother tongue) and the handwriting mode(which is quite good), is not available in most other apps.

I had thought about turning on the clipboard history option and am thinking about the privacy/security aspect behind it. As per Gboard, it remembers history for 1 hour and there seems to be no sync option. So it seems sort-of safe. Thinking about such things since I do copy-paste OTP's.