Reproduced on at least SFF and MSE, on:
- Windows 10, Firefox 74.0, logged in
- Android 5.1.1, Chrome 80.0.3987.132, logged in
- Windows 10, Microsoft Edge 44.18362.449.0, logged out (by copy-pasting a link with the
Clicking on the
/?lastactivity links does not redirect to the latest activity, only to the question; for instance, if I click the following, I'm redirected to the question itself, not Robert Longson's answer.
I do have some userscripts running on Firefox, but none on Edge or Chrome for Android.