Change #1149708 had a related patch set uploaded (by Jdlrobson; author: Jdlrobson):

[mediawiki/extensions/Echo@master] Fixes: loading of Echo on mobile domain for Vector 2022

https://gerrit.wikimedia.org/r/1149708

Does Echo still need a separate mobile mode?

A few years ago, we made the desktop mode popup behave better on small screens: T287132#8590649

And more recently, I made it possible to display the mobile-style combined badge without using a separate mobile mode: https://gerrit.wikimedia.org/r/q/topic:echo-combined-badge

How far are we from deleting the 'wgMFMode' check and 'ext.echo.mobile' completely, and just using the same interface everywhere?

The mobile version has browser back button support which is important for mobile devices where it's expecting that back button allows the user to escape the overlay. I think at minimum the OOUI based overlay needs to support that too.

A few years back it was important for notifications to mirror the mobile main menu and slide out from the right and for it to be larger on tablet devices. I assume that's still important.

How far are we from deleting the 'wgMFMode' check and 'ext.echo.mobile' completely, and just using the same interface everywhere?

I'd say not far, but that requires it to be a product priority and I'm not sure it is that right now given what's in the annual plan and doesn't have an team actively maintaining it (the latter I'm still working on).

Change #1149708 abandoned by Jdlrobson:

[mediawiki/extensions/Echo@master] Fixes: loading of Echo on mobile domain for Vector 2022

Reason:

Not a priority. Will come back to this at a later date.

https://gerrit.wikimedia.org/r/1149708