As shown in the image below, the new experimental sidebar has been activated. This allows easier navigation of the forum plus allowing the end-users to pick what category’s and tags they want to show on their sidebar (accessible under their settings).
I also altered the default homepage to be Latest as it makes more sense this way, if you would like it to still be the other way around and have it be the Categories homepage, you can change that in your settings as well.
IMPORTANT EDIT: It has come to my attention that enabling this feature may put old posts in your tracked,watching lists aswell as sending you old notifications. If you clear those in your settings and dismiss all notifications it should not happen again as it was just the activation of the sidebar.
Not sure about changing the default homepage now to something else, i.e new, latest, or top. Users would still be able to pick what they want as their starting page in their settings.
As said above it most likley just because of this new feature added, I suggest looking at your tracked,watched posts, getting rid of what you don’t want and dismissing all notifs. Hopefully you don’t get any blast of notifs from older times after that.