Or ESC followed by "." Repeating it works too.

You will need to wrap the third argument to keymap.set in a function, like so:

vim.keymap.set("n", "ff",  function()
  builtin.find_files({hidden=true})
end, {})

In my previous main keyboard the halves were connected using USB-C. However, I've currently switched to a piantor with TRRS.

I really liked the idea of USB-C: same connector everywhere, more data lines and no risk of short circuit during connect/disconnect. In practice soldering USB-C connectors was not easy for me, I encountered continuous issues and had to resolder them multiple times.

While my soldering skills are not great, I can reliably solder TRRS. I prefer having a reliable connection even though I have to pay attention to connecting and disconnecting it when the keyboard is not plugged in.

Just sharing my experience, I wish I could solder USB-C connectors reliably.