Yup, verified fixed as far as I can tell. Signing in at https://mail.yahoo.com/ in latest Firefox Nightly on Android, I end up at https://mail.yahoo.com/m/ , the "good" URL noted in comment 1, with e.g. stars at the right side of the screen for each message (matching the Chrome experience in comment 0's screencast).
Bug 1892697 Comment 5 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Yup, verified fixed as far as I can tell. Signing in at https://mail.yahoo.com/ in latest Firefox Nightly on Android, I end up at https://mail.yahoo.com/m/ , the "good" URL noted in comment 1, with e.g. stars at the right side of the screen for each message, and with the searchbar staying fixed at the top of the screen as I scroll (matching the Chrome experience in comment 0's screencast).