This is a drop-in replacement for Pichaxx that's already been around a good while:
https://github.com/zoogie/Bannerbomb3
You don't hear about bb3 much because it's not the official "guide method" at this time, but it could be deployed after the eshop closes if its needed.
Like Pichaxx, it's free and set up with Seedminer. but unlike Pichaxx, bb3 is built into the system and doesn't need eshop at all.
The current variant of Seedminer itself has an online component, but that (friend service) should persist long past the eshop. And if it doesn't, there's at least two good offline options, one known (Mii QR bruteforcing), and one unreleased (APthief).
And on top of all that, there's a free offline primary that I'm working on that is not a done deal, but getting more promising every day.