We did have a look at what would be needed to add portal support in Chromium, on the basis that this would eventually percolate through to Electron:
https://bugs.chromium.org/p/chromium/issues/detail?id=981309
Similar to that Electron PR, there was similar push back against simply porting over to GtkFileChooserNative, over concern for supporting old versions of GTK. Rather than using dlsym to check for those symbols though, the Chromium developers seemed to think coding directly to the portals D-Bus API would be a better approach to remaining compatible with those old systems. Nothing has really progressed on that front for a while though.
As far as camera/audio portals go, that is currently tied in to PipeWire. I suspect Ubuntu will eventually adopt it, but we are not there yet. It’s also requires modifications on the application side (somewhat simpler if they’re accessing devices through a framework like GStreamer).