I bought Minecraft Java edition a few years ago. From Mojang account, I changed to Microsoft account, I installed a new launcher from the Microsoft store, I logged into my account and saw the text play Minecraft Java edition demo.
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Thank you for your report!
We're tracking this issue in MCL-20216, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as Fixed. Please check the Fix Version/s field in that ticket to see in which version this behavior was or will be fixed.
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