How do I sign out of a Microsoft account on Minecraft Windows 10 Edition?

Sign in the Microsoft Store with the old account. Then, install "Minecraft for Windows 10", it should be free. After that, sign out your old account from the Microsoft Store. Open up "Minecraft for Windows 10", then sign in with your new account. You will
get updates for free if you do the following. I hope this helps.

Hi, I hope you're doing great out there despite the issue that you're experiencing. I am an Independent advisor and I am here to help you in regards to your concern.

If I may ask, what Minecraft version you have purchased? Is it Minecraft for Windows, or Minecraft Java Edition?

If it's Minecraft for Windows, simply sign out your account on Microsoft Store then restart your PC before signing back in.

If this is Minecraft Java Edition please do the same, sign out on your Microsoft Launcher then restart before signing back in.

Let me explain. Minecraft was bought in the Microsoft Store using a different account. Then that account signed out and my account signed in. I am 100% certain that I bought the full version of Minecraft Windows 10.

(EDIT) Also, it's the DEVELOPMENT beta, like the Xbox Insider Hub beta.

Here is an explanation. But it may be a bit advanced.

https://answers.microsoft.com/en-us/windows/forum/windows_10-other_settings/minecraft-windows-10-xbox-log-out/cd1f0a33-5743-4ab0-9bf5-b09f9a5a453f

Hope it works. Happy gaming!

-Cassie

Players who already have the previous PC or Mac edition of Minecraft (running on Java) can
download Minecraft: Windows 10 Edition for free.

Note You'll need to get a code from Mojang, the game developer, by signing in to your Mojang account before attempting to redeem your code for Minecraft: Windows 10 Edition. Otherwise, you
may incur a charge. To get your code from Mojang:

1. Sign in with your Mojang account.
   
2. Under Minecraft: Windows 10 Edition, select the link to request a code. Microsoft Windows 10 will open.
   
   Note You'll need to sign in to or create a Microsoft account. If you sign in, use the Microsoft account you use to sign in to your Xbox account.
   
3. If you're running Windows 10, you'll be able to download the game right after redeeming your code. If you're running an earlier operating system, you'll need to come back to Microsoft Store once you're running Windows 10.
   

The code you receive from Mojang will be kept on your account, in case you’re unable to redeem it straight away, or in case you have problems trying to redeem it in Microsoft Store.

For more info:
https://support.xbox.com/en-US/games/game-titles/minecraft-windows-10-edition-faq