zxcvbob wrote:

....
The bigger problem is finding crimp sleeves that are appropriate for
joining copper and aluminum. Tin plated might be compatible with both
metals, I'm not sure.

That's where I'd think the problem lies, too...and if one is looking for
NEC-approved or equivalent as I thought OP was, that could be a problem.

I guess NicoPress would be one place one could start looking...we use
them on electric fence, but that's not the same thing by any stretch as
for residential wiring...