Tool free? Wago connectors, wire nuts, twist-togther-and-insulating-tape and similar things I wouldn't want to use on a bike other than as a roadside bodge.
Minimal tools? Choc blocks, butt crimps, spade connectors, jelly crimps, Tamiya connectors, Weatherpack, etc, etc. Some crimp connectors are lot more tolerant of crappy crimping tools than others, so if you're just abusing pliers, I'd stick to the less fiddly ones.
Soldering iron? Direct solder-and-heatshrink splice would be my preference, unless you really need the ability to disconnect. Many connectors designed for crimping can be successfully soldered if the joint won't be repeatedly flexed (solder tends to wick up stranded cable and make it brittle).
FWIW, on my recumbents I've shortened the input wire to a similar length as the rear light output and used spade connectors to join to the cable run down to the dynamo. The junction can be cable-tied to the light bracket, so it doesn't flap around in the breeze.