Depends on the miles. An EV undertakes a new gas car after 20k miles.

There is a point where a new EV, with mined lithium and all, will be more environmentally friendly than a used car that didn't need to be built but burns gas for every mile.

If you live in a sunny area (pv) or a dense hydro area, that point is quite quickly reached.

Whether there's a net lower carbon footprint depends heavily on how much gasoline you burn

However the used EV market is only growing

Simple to do badly, but still challenging to do elegantly. Managing power/throttle response in every situation is quite complex if you want it to feel good. Kinda like how everyone makes a trackpad, but only Apple makes Apple trackpads.

And thats before we get into the complications of thermal management with the batteries and heat pumps and stuff.

Do you mean for an ICE to EV conversion? You can already buy such kits.

And fewer moving parts means less expensive maintenance, generally. Granted, replacing a battery can get expensive, but if you're not going all that far anyway, the battery's range dropping from 400km to 200km after 12 years or so might not be a big deal. That said, the boots theory of socioeconomic unfairness might mean you're stuck with ICE vehicles for a while if you can't get a loan for a comparable amount of time.

Edit: after looking it up, that's also assuming a worst case loss, average range is now roughly 460km, getting better, and it's still at ~78% capacity 10 years later.