If you're rocking a native TRMNL device (not BYOD, not Virtual), you can unlink it in 1 click. Then you just need to perform a 'soft reset' on the device itself.
Here's how.
Step 1 - Visit the device settings
Inside TRMNL, hover the top-right dropdown and click the gear icon beside the native device you want to unpair.
Scroll down to the Unlink Device section and click "Unlink."
After confirming the scary confirmation box you should see a success message:
Step 2 - Soft reset the device
Now that the web application has said farewell, we need to instruct your physical device to consider itself reborn.
Assuming your TRMNL is already on, hold the button on the back for 5-7 seconds, then let go. This should re-enter WiFi pairing mode:
Next, connect to the WiFi network named TRMNL as the screen suggests. You can do this on a phone or computer.
But wait! Don't choose a WiFi network. We're resetting it aren't we?
Ignore the network list at the top, and simply tap the "Soft Reset" button near the bottom. Then tap "yes" when it asks you to confirm.
Step 3 - You're done!
Within a few seconds, your TRMNL should re-enter WiFi pairing mode for a 2nd time. But this time, it will be as if it's a brand new device.
Your previous user connection, API key, Friendly ID (6 digit code), mirroring settings, name, refresh rate, sleep settings, and so on, will all be cleared.
You may now set up this device like usual, or turn it off and give it to someone else.