This isn't a bug, but a feature request. There's currently no DRM support on manjaro arm, as mainline manjaro seems to relly on some AUR package to support sites that depend on DRM (I don't remember the package name.) I believe the issue was raised on these forums, but went undetected by developers, so into a bug section it goes.
What DRM do you mean?
If you mean widevine DRM the reason is simple.
Widevine is an x86_64, i686 and armv7h only library.
Manjaro ARM is an aarch64 only distribution.
@spikerguy has made a package "chromium-docker", which is a hacked together way of actually using DRM content on Manjaro ARM, via an armv7h docker container with chromium and widevine.