Waterproof jacket and trousers that fits a pannier bag (preferably waterproof also) makes you basically 90% rainproof, especially if the trousers have shoe covers or your shoes are at least a little waterproof. Also, clear glasses avoid raindrops to go into your eyes while riding and allow you to see the road. Like this, only your hands are not covered.
Different apporach: use the keyboard you like and block its internet access using invizible pro/netguard/afwall.
I had the same problem, after using openboard for a long time, and now I’m doing this, using gboard and blocking it with invizible pro.