Would an LG Aristo Factory Reset Fix App Issue?

I wouldn't do a factory reset for the this. If there is a solution it will be less drastic than that.

The first thing to ascertain: is this a bug, or is this the way the current version works? I'm not quite sure what I'm looking for: the "Active tab" shows friends who are currently active, which doesn't seem to be what you are asking for. So if there is a toggle to change your status (which I think is what you are after) where should I look for that? Because I've had a look on my phone and if there is such a toggle they aren't making it obvious. This is important, because if this is just the way the app works now your solution is to revert to an older version or switch to Messenger Lite, neither of which requires a factory reset (and a reset won't help).

If you need to revert to an older version, you can find that at apkmirror.com. Download the apk from there, turn on installation from unknown sources, uninstall the current one, install the one you downloaded, and never update it (turn off automatic updates before doing any of this, if you have it on). If the app was pre-installed on your phone so you can't uninstall it, uninstall updates instead (which will revert you to the original version) or disable and then install the version of your choice from apkmirror.

(I would normally advise against installing apps from random sites on the web, but apkmirror is generally regarded as trustworthy).

If it is a bug (i.e. if the feature should still be there but isn't working on your version, and I've just not worked out where it is) then there's no need to reset the whole phone. Just clear all data for the Messenger app, or uninstall and reinstall. Worst case try going into recovery and clearing cache (just cache). Between those you've done everything that a reset would do as far as Messenger is concerned, without the hassle of having to set up everything else again after a reset.

Do your friends have exactly the same version of the app? I can't see such a button on mine (which is why I was asking you where it should be, just to be sure it's not hidden in a corner of the UI I've not looked), and my version is 145.0.0.25.203.

I don't know whether it's a bug or not, but then I'd not noticed such a button before. I could perfectly well imagine FB themselves removing such a feature (they want people to be interacting with FB all the time, after all). But a bug is more likely to result in a button that doesn't work than no button at all, so my money is on it being deliberate, one way or another. I don't know whether android version is relevant, but just in case I'm running on 8.0.

I suppose I could dig my old phone out, which won't have been updated for a month or so, and see what version it is running and whether it has such a button (and if it has, update it and see whether it goes away after the update), but I can't really do that at the moment.

I doubt the OS version matters, I was just thinking about what other variables there might be . I'm sure that an OS upgrade won't change anything: I don't seem to have this either, and I'm running 8.0.