Multi-carrier SIM for the USA?

Any recommendation for multi-carrier SIM in the USA, to use either AT&T or Verizon ?

Verizon uses CDMA AFAIK. No SIM

Not anymre. CDMA applied to 3G and earlier networks. With the move to LTE and beyond, CDMA was deprecated. It is no longer in use.

Verizon uses SIM cards now (although there are many phones with built-in SIM (eSIM) cards, so it might appear otherwise).

That said, @reinerotto - two thigns:

  1. I'm not aware of any dual-carrier SIM cards that can use AT&T + Verizon in the US. The wireless carriers just don't cooperate like that, and you need to get a SIM card directly from the carrier to use it on their network.

  2. This is fairly off-topic for the OpenWrt forums, even if the SIM card might be inserted into an OpenWrt device with a cellular modem... this is really a better question to ask on forums that deal with cellular service provider related topics.