Please check if this helps:
1. Create a button

2. In the flow, initialize your variable where you want to store the Button Text property. Use "Ask in PowerApps"

3. In the PowerApps button, attach the flow and on OnSelect write the following code:
PowerAppsbutton.Run(Button1.Text)
where PowerAppsbutton is the name of the flow.
Output:
When you click on the button, the flow will run and get the name of the trigger button:
