Disclaimer: MHT does not condone piracy. Use this guide with caution.
Disclaimer: This tutorial is out of date. I have made attempts to update it sufficiently, but am unable to. Trying to follow it directly may result in issues.
There is a version of Minecraft Bedrock that is designed only for Mojang developers and marketplace creators. It was leaked. Microsoft, being Microsoft, tried to remove it from the Internet, but the Internet is always faster than the corporations.
Step One
Download the zip file. The link is to a message in a Telegram group, so you may need a Telegram account.
Step Two
Extract the zip file's contents. You'll end up with a folder with 2 files in it:

Step Three
Go to your start menu and search for "certificates". Open this app:

There will be an administrator prompt. Click YES.
Step Four
Open the Trusted Root Certification Authorities folder you see.

Step Five
Right-click anywhere on the screen and go to All Tasks > Import...
This message box will appear:

Click on NEXT.
Step Six
Click on Browse... and find the certificate.cer file that was included in the folder you extracted. once you've found it, select it.

Click Next and then Next again. After that, press Finish.
The certificate for the APPX file we downloaded has been accepted by Windows and it won't scream at you.
Warning 1
You need Minecraft already installed for this to work.
Warning 2
Disconnect from the Internet before opening it. This is because Mojang will attempt to lock you out of playing this build of Minecraft.
Warning 3
You might lose all your worlds installing this. To back them up from in the game, click on the pencil next to the world. Then, go to the bottom and press export world. This will export the world to a file you can double-click to add to the game.
Step Seven
Go back to the folder and find the Minecraft.Windows.DEBUG.appx file. Right-click it and press INSTALL.
Step Eight
Click on REINSTALL in the screen that appears:

Step Nine
Click on REINSTALL to confirm your choice.

After it installs, disconnect your device from the Internet and launch Minecraft Dev!
Kudos to IllusionerC, who originally posted this file, and someone else downloaded it before it got taken down and uploaded it to G Drive.
Yay. 2022.
The G Drive link is down, just go to the following Telegram group:
Telegram: Join Group Chat
It will contain the link to the official MCDEV website, and will let you download any MCDEV version you wish for.
PS It took me forever to get that.