There’s a lot of options out there, I’ve seen some really fancy ones with a lot of bells and whistles, but my personal experience is that most of the ones I see people buying and installing are pretty basic mechanical devices hooked up to a water line with no electrical components. Just pieces of plastic and/or metal being acted upon by other pieces of plastic/metal and water pressure.

Most people are retrofitting them into existing bathrooms, often they don’t have convenient electrical lines/outlets close enough to their toilet for a clean-looking install and don’t care enough to run them, and needing to recharge or replace batteries in their toilet isn’t something they’re particularly interested in doing (I fall into this category myself)

Personally I have 3 toilets with 3 bidets, all basic cold water models with no other features. None of them have convenient power, I’d have to run a cord to the outlet by the sink, or run a new outlet for them. It’s certainly doable in all 3 cases, but more work than I care to put into it, and I’m too stubborn and cheap of a DIY homeowner to hire an electrician for something I could do myself. One of them is close enough to the sink that I could run a hot water line to it without too much bother, but that bathroom is pending a renovation so I’m waiting to see how things look when I get into that before I do it (that bathroom is also furthest from the water heater, so you usually have to run the water for a while before it starts coming out hot from the tap, so kind of less than ideal and maybe not worth it)

On that note, cold water bidets are a little unpleasant at first, but you get used to it really quickly, and if you’re kind of a fat sweaty guy like me they’re actually pretty refreshing once you’re used to them.