We won't go into details about trucks, truck parts, different truck sizes and shapes, baseplate angle... If you want to know more, there are plenty of articles on the internet, check this one, this other one, this technical one... Here, we'll just do a small recap on trucks for esk8s.
Electric skateboards trucks
As electric skateboards are often based on longboards, and used at higher speeds than regular skateboards, esk8 trucks are almost always longboard trucks, either commercial ones that you find in any longboard shop, or specific ones made only for esk8s.
In the world of assembled esk8s, the trucks used depend mainly on the esk8 price. A cheap esk8 will use cheap chinesium trucks, probably copied from a known truck brand. They are good enough for beginners and lower speed. But they can be dangerous, the axle can bend, or even break. And you don't want that to happen while riding at 20km/h. High-end esk8s use trucks from specialized brands, allowing for better performance, better tuning, safer for higher speeds (40km/h+).
The DIY case
When building your own esk8, it's a bit more exciting, as you can choose the brand and model you want. The only condition really is that you need to be able to make it work with the drivetrain you want to use.
The common belt/pulley drivetrain doesn't require any modification on your truck, as long as you find a motor mount adapted to the hanger shape.
The most commonly used trucks are the Caliber II trucks. They have a hanger with kind of a square shape that makes it easy to attach a mount that won't move around the truck, and they are fairly priced. A lot of Caliber II clones are available on the market too, for the same reason. But other brands/models also have that handy square-shape hanger.
Other trucks can also be used, you just need to find a mount that'll fit. There are dozens of mounts out there, people even make and sell their own, so you should find something that suits your need.
Hub motors as well as direct drive drivetrains require specific kind of trucks. Some people modify standard trucks for doing that, but it's not a job everybody can do. You often buy your hub motor with the truck, same for direct drive.
If you're not happy with the way your truck behaves, don't forget that you can tighten or loosen the bolt on the kingpin. If it's not good enough, you can actually buy bushings with different durometer (softer or harder), which might help. Bushings can also loose their capabilities with time and wear. If you want to know more about bushing, you should read this article.