thermite is a real diy compound. all you need is a file, some rusty iron and some aluminum. and the magnesium strip for the catalyst/fuse.

I suggested thermite because it's so easy to make. Check this source. Print a canister, add a strong capacitor as ignition which engages when the release servo turns on. Really the simplest homemade burning device which burns through everything.

What trace is there when you download a drone model somewhere? Loads download these. Use TOR to be extra safe. Getting the sensors, motors and wires is also easy and untraceable. A while ago journalists managed to order 4 handgrenades after searching 30 min on the dark web, which got delivered. There is so much junk coming from Asia through websites like aliexpress. I recently ordered a bunch of arduino myself. It's so easy to get what you need, untraceable, and building and printing a drone is also super easy. Controllers can be bought off the shelf too. A release and fire mechanism is also super easy: a 85 cents servo.

I've seen Ukraine make these drones from wooden twigs or plywood, with a print plate, 4 motors and printed rotorblades, and a servo as the release mechanism. You're not printing gun parts, you don't need specially produced parts or machines to start with.

With an ESP32 you can even add a 12 euro camera which will auto guide itself to its target so you don't even need to control it. The code is freely available, training it would need a few photos of the target. Total costs would be ~50 euros, all build plans and code is free available online, as well as all the tutorials for soldering and uploading the code to the boards.

About the digital footprint: Just order stuff with a fake name, pay with gift cards bought with cash in stores ( like PayPal or aliexpress gift cards) ship it to a DHL pickup point, wear a cap and sunglasses when picking it up. Never bought drugs online? Or go to a hobby store for remote controlled stuff or an electronic parts shop. And maybe don't buy everything from the same place and buy other stuff too. Have fun looking for the right guy while loads of people order generic electronic parts online. It's like searching for a drug dealer by checking everyone who ordered plastic bags online.