Sharepoint button to run a Power Automate flow.

I'm still new myself and have a similar question. As with most Microsoft things, you may need to devise a nonsensical workaround. Here's the best solution I've been able to integrate into our workflow.

Install and sign into the Power Automate app on your phone. You should find your button on the Buttons page. Select [ ... ] and choose Share Button Link. This will give you a url to access your workflow. Copy this url and open it on your computer's web browser.
Depending on where you want this, you can usually find a place in SharePoint to create a link using this url. I have a weblink in a SharePoint Document Library which I've pinned to the top of the library for easier access. I also have the link on various buttons on our Hub Site homepage.

To my knowledge, someone please tell me otherwise, the Power Automate app is the only place to find the url to the button.