Obviously, a single solid axle connected straight through the wheels would bend if the wheels to which is was connected were to rotate right or left with respect to a vertical line (i.e. be steered). I’ve watched an explanatory video on the rack and pinion mechanism and how power steering augments this, but it didn’t show a mechanism by which the steerable wheels could also themselves be provided power. How can an engine provide power to wheels which are not perpendicular to that engine or the axle?
You could also include front-wheel drive in your question. It would be enlightening for you to look at what radio control rock crawlers do. It has much of the excess of a full-sized car stripped away.
But they are all basically variations of the universal joint. The variations come in different names with different tradeoffs: actual universal joints, dogbone joints, CVDs shafts, etc.
Universal Joint: https://www.rpphobby.com/product_p/irc00220.htm
Something like a universal joint will have speed oscillations as the angle moves away from zero such that for a constant speed input, the output will slow down in certain parts of the rotation and speed up in others to catch up.
Most full-sized vehicles would use a CVD joint though because CVD stands for constant-velocity drive.
And there's more than one way to build a CVD: https://www.kmpdrivetrain.com/driveshafts/blog-tripod-vs-rzeppa-joint/
A second hiccup you might not have thought of is that the wheels ride on suspension arms so their distance from the differential might vary. Notice the telescopic shaft on some models while other models have a dogbone which can slide back and forth. Apparently this sliding or telescopic action is also necessary for the constant velocity aspect.
Also note that similar mechanisms are needed to transfer engine torque between the front and rear wheels since they are on suspension and thus will vary in height between each other and the engine.