r3dfox is a modern Firefox based web browser for Windows Vista & 7. SourceForge link for downloading with older browsers. https://sourceforge.net/projects/r3dfox/
I do not build with Widevine or EME/DRM. I haven't tried to see if it's possible, but some older builds might have it. I suggest asking if @Alex313031 could do it in Mercury-Win7.
It is possible this to be fixed or with unsigned drm it's not possible, as I understand recently.