Many of Hank's lights do have the pogo pin interface and he sells the programming adapter:
D4S2: https://intl-outdoor.com/emisar-d4sv2.html
Reflashing kit: https://intl-outdoor.com/components-6/gears/reflashing-kits.html
I believe a few of the new Astrolux lights have it to, but there's a different pin configuration. Here's a pic I took of the FT03 Mini showing the pins in the upper left:
Again, you have to match the software to hardware, but yes - you can buy a light with Anduril and change it to something else. The good thing is Narsil and Anduril were designed for the ATTiny85 MCU so they are usually compatible. I say "usual" because depends on the hardware. Anduril also supports more MCU's than Narsil does.
More info on programming/reflashing keys/adapters here: https://budgetlightforum.com/t/-/72815