Use PowerShell Script

Pinning steps:

• Run shell:start menu
• Go inside the Programs folder
• Create a short cut to powershell -c start vivaldi https://some.app.com
  • Don't use —app=https://some.app.com, no tab bar
• Right-click the shortcut, choose properties to change icon
  • Type shell32.dll for some basic icons by Windows Explorer
• Right-click the shortcut, choose pin to Start
• Open Start Menu scroll to the shortcut, choose pin to Taskbar

Use Edge Browser

Pinning steps:

• Main menu (3 dots)
• Click More tools
• Click Pin to taskbar

Any Chromium-based Browser

This solution fails, it pins the browser itself (never the web app icon), not the browser pointing to the app.

Run the Web App

vivaldi https://some.app.com

• Note that the URL to web app must be a full URL with http or https.
• Don't use —app=https://some.app.com, no tab bar

Pinning

Steps to pin to taskbar

• Right-click the app icon on taskbar just launched
• Choose Pin to Taskbar