What can I do to regulate iPhone charging rate (make it charge slower)? My iPhone is charging from my MacBook. I believe that it charges too fast and even heats quite sensibly. Also, I'm afraid the battery could degrade at a greater rate with such a fast charge.

So, I don't need that fast charging, because it has plenty of time to charge.



As you can see, the battery temperature rises quite a bit.

By the end of the charge, the temperature drops to 30 degrees.

I'm well aware that there's a new thing that analyses how much time you let the phone be on charge and slows down the charging rate accordingly, but only after the battery reaches 80% (more details here - https://support.apple.com/en-us/HT210512)

What can I do apart from just buying a cheap charger? (I don't think it's a great idea)
Fast charging your phone via a MacBook is not going to "damage" your battery anymore than other kinds of charging. Yes, high temperature can affect the battery, but a temperature of 38 degrees C is not a problem in charging your phone.

There's no need to limit the charging rate beyond what the iPhone does automatically by itself.

Also there's no setting in macOS that will allow you to limit the power supplied to the phone charging through a USB port (besides limiting it to 0 by turning the port off completely).