fencedframe: https://developer.chrome.com/en/docs/privacy-sandbox/fenced-frame/
controlledframe: WICG/proposals#88

The fencedframe and controlledframe tags are very similar to the webview tag in Electron: they are all isolated iframes running in their own processes, and they behave like top frames. I believe lots of existing users of webview tags can migrate to these tags, which will be very helpful when we have to remove webview some day in not-very-far future.

The fencedframe and controlledframe have already been implemented in Chromium, though still being experimental. The fencedframe tag is available to all web pages, but it is currently behind some flags and require the web page to send a special header to be able to be displayed. The controlledframe tag is only available for Isolated Web Apps (IWAs).

Exposing them in Electron does not take much work, but before doing that I'm interested to know if users would really be interested to use them.
/cc @electron/wg-api @deepak1556 @miniak @Kilian