Hi, I'm pretty sure I'm seeing this too. I'm running it under apache2 and with mariadb.
After a week or so uwsgi was using about 7% RAM on an 8G machine. I restarted mailman3-web and that went back to 1%. One day later it is up to 1.2%; I guess it will keep growing and I will also have to regularly restart mailman3-web. Is it easy to switch the mailman3-web package to run under gunicorn? Cheers, Andy