It's built into the Chromium based Edge which is actually a great browser in many other respects as well. Particularly fond of how easy it is to install any arbitrary web app as its own dock/taskbar icon at my own choosing vs the wall of prereqs [0] Chrome puts up before allowing the same.
After the HN post about this last week I switched to Auto Tab Discard [0] based on other people's suggestions and it's been perfect for my needs. I hate to lose the Great Tab Suspender if only because I liked the UI/character/branding but other than that I haven't noticed any differences or issues since moving to ATD.
https://blogs.windows.com/msedgedev/2020/12/09/sleeping-tabs...