Where to place .Xresources on modern systems?

According to some old documentation about mwm, many settings for this window manager must be placed in an .Xresources folder in the $HOME directory. When I normally boot up my computer (Debian 11), mwm appears to ignore and not load the settings in ~./Xresources. I found a word around is to type xrdb -merge ~/.Xresources, but I'd like a permanent setting. What is the proper way to configure mwm on modern systems where ~/.Xresources is no longer used.