I have been having serious server browser issues for a long time now, and I know I am not alone as the group of 10 friends I play with all report the exact same issue.
Basically, the server browser doesn't work, no matter the filter settings. At default settings, if I search for servers, I get flooded with 90% dev branch servers (all empty), and about 20 regular servers, most of which are empty, with 5 or so populated, and only 1 or 2 at max population.
If I filter for minimum players (say 10 or so), and also filter passworded servers, then my search results come back with 10 or so servers, or less. I know there are more servers than that, with higher populations and stable pings. I know this because if I put in the name of a particular mission I know of (wasteland, for example), I will get every server with that mission name, and all within the boundaries of my previous filter settings, but they just wouldn't show up until now.
This makes it impossible for me to find new servers and game types, because they don't show up in the regular server browser, and thus I am unaware if they exist or not. This is hilariously broken and I have no idea how to fix it, or if it is even something that can be fixed on my end.