Each country within the EU is responsable for their voting system and each country has their own and most are exclusively offline. The EU initiatives is an EU system and has nothing to do with the countries voting systems.
I use it with a friend that's really concerned about security and privacy. The only downside I've faced is that adding contacts its kinda bodersome if you're not fisically together.
It's supossedly used by the French government, so I guess it says something about its security and privacy.
There are options. Some IOT things are even DIY with open specifications and open firmware, so you can build and repair them yourself. And a lot of times it's the cheapest option, way way way cheaper than the usual IOT stuff, as most electronics used for IOT are dirt cheap.
I like both. I prefer KDE for keyboard and mouse use and GNOME for touchscreen use.