Additional features, settings, or issues not covered by specific Microsoft Teams categories
Unfortunately there is no way to change this behaviour. You will either need to use the format button or hit SHIFT+ENTER. I would recommend communicating with your users to educate them on the two options.
However, you could submit feedback to Microsoft and see if they can add an option at https://feedbackportal.microsoft.com/feedback/forum/ad198462-1c1c-ec11-b6e7-0022481f8472
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