This was created with the intention of helping people who have trouble with calling stratagems, either due to hardware limitations or accessibility limitations. This WAS NOT created to help people win "Stratagem Hero", but do what you like with it.
DISCLAIMER: At any time the Helldivers 2 developers could update Helldivers 2 and break this. Do not rely solely on this. Also, since there is anti-cheat with this game, there is a chance that you could be flagged. Many people are using systems like this in Helldivers 2 and there haven't been any reports of bans at the time of writing, but use at your own risk.
INITIAL SETUP
Step 1: Make sure you have the latest version of the Elgato Stream Deck software installed
Step 2: Download the Stream Deck profile from the Elgato Marketplace (or from the Discord if you have early access). Extract the ZIP file.
Step 2a (optional): By default, the profile you download will have the HOME
key set as the key that opens the Stratagem Menu in game. If you'd rather it be a different key, scroll down on this page to the Modify Your Stream Deck Profile (BETA) section, select which key you'd like it to change to in the profile, upload the Helldivers 2 Stratagems - 15 Key - [version number here].streamDeckProfile file then press the "Reconfigure and Download" button. It will then modify the file and download the file for you automatically.
Step 3: Open the Stream Deck software, then go to your downloads and double click on the Stream Deck profile file you've downloaded. In the Stream Deck software, select which device you'd like it to be installed on.

Step 4: Press the icon with the wrench on your Stream Deck to go to the configuration folder. You will see arrows and what looks like a menu button. These are your Stratagem keys that you have to bind in Helldivers 2. Once you bind the keys, you can either just stay on the Configuration page and manually enter Stratagems (if you aren't able to for some reason with your existing hardware or want to use the Stream Deck just because you like the buttons better than your keyboard or controller buttons) or you can continue to use the Stratagem mapped keys. Go to the Menu Screen > Options > Mouse & Keyboard > Change Bindings then scroll to the Stratagems section at the bottom. For the Open Stratagems List key, change the first box from Hold to Press. Then click the second box and when it says Press Any Button, press the button on the Stream Deck with the 3 lines (like a menu button). For this profile, it sets the Open Stratagems List key to the HOME
key by default, but it will be different if you reconfigured it in Step 2a. Then set the Up, Down, Left, and Right keys using the Stream Deck buttons.
Step 5: Spread Managed Democracy!
NOTE: If you have a Stream Deck with less than 15 keys, or you want to build your own profile from the ground up, use the all-new Drag-And-Drop Builder. You still have to reassign your Stratagem List button in the next step, but then go to the new section to see how to use the Drag-And-Drop Builder.