There is no application set to open the URL

Miro actually has a Help article to solve this issue: https://help.miro.com/hc/en-us/articles/360019244239-How-to-Disable-Miro-Desktop-App-Pop-up-in-Your-Browser

Here's the important steps:

For Mac users

Step 1. Delete (uninstall) the Desktop app from your computer.

Step 2. Rollback the setting ‘Always open URL in the Miro App’ in your browser. Here's how you can do that in Chrome and Firefox. For Chrome:

• Close all Chrome + Miro windows before starting (use Cmd + Q to quit the browser)
• Open a finder window > press Command + Shift + G > enter the following path into the search box: ~/Library/Application Support/Google/Chrome/Default/Preferences.
• Open Preferences in a text editor Search for https://miro.com":{"miroapp":true}
• Remove https://miro.com":{"miroapp":true} Save changes Restart Chrome browser.

If you use several Google profiles, you will need to edit Preferences in all catalogs. For this, on step 2, you will need to open ~/Library/Application Support/Google/Chrome and change Preferences in folders Profile 1, Profile 2, etc.