It probably varies between EV manufacturers, but my Tesla Model 3 has been the easiest vehicle to self maintain that I’ve owned yet. Mostly due to how little maintenance there is, but also because of the completely open and online factory service manuals and parts manuals.
It’s ridiculously easy to look up a part number, order it online from wherever is most convenient, and follow the steps in the manual to replace it.
I had the opposite experience with my 10-year-old Model S.
Most parts could only come from Tesla, including the Bilstein struts (a part number Bilstein refuses to sell to anyone but Tesla). $900 per corner.
USB port between the console? $400. I found a used one on eBay, fortunately.
When the wheel rotation sensor receiver went bad, it cost $2500 for them to install and reprogram the replacement, because they "upgraded" to a different mfr. When that one started to go bad (water ingress, which wasn't cured by the new part), I sold the car and said good riddance.
It’s ridiculously easy to look up a part number, order it online from wherever is most convenient, and follow the steps in the manual to replace it.