I always use an IPad to view the forum. I don’t get to see the three lines when I use that. I have seen those lines on my phone though.
The only way I can see the most recent activity is to click on a bell in the upper right. I will see responses/reply’s as well as any other activity on the individual threads I’ve commented on. That is only good for a few threads and it doesn’t show any new conversations. It also shows every “like” a comment gets so I think it get’s overwhelmed with those and the list stops loading more after a couple of threads.
The only way I found that works for me is to select the “All Discussions” heading. You then see the threads but you also see the person who started the thread. If you immediately hit the reload arrow in your browser that page will reload but now it will say the name of the last person who commented and the time they did instead of its creator. That’s the only way I have found that works for me. The bell route doesn’t really work.
I wouldn’t say the way I do it is easy or particularly efficient but it is what it is.