I have found no problem with MWB v4.0.4 Free installed alongside Avast Free 19.8.2393 (build 19.8.4793.545) on Win10 1909.
I have all the MWB real-time protection (Premium & Premium Trial) switched OFF, as I only use MWB for occasional manual scans.
Also had no problems with MWB3 setup this way, prior to updating to MWB4.