TBH, getting WideVine to work in Chromium is as simple as 'poaching' the
WidevineCdm directory from a current copy of Chrome, and just dropping it into the main 'chromium' directory. If Chromium is asked to open a site that requires DRM, it'll find it and pick it up automatically.
The reason this works? Simple.....because Chromium is the default code-base from which all the other 'clones' take theirs. Even Chrome; it, too, is a 'clone' of Chromium, albeit with Google's own, proprietary, 'nosy', tracking/telemetry stuff added to it.
When Chrome was announced back in Autumn 2008, they set up the Chromium Project at the same-time, as a publicly-scrutinised, open-source entity. The Project is essentially Google's browser R & D department, with semi-autonomous 'build-bots' churning out dozens of updated builds every 24 hrs. Every time a 'patch' is submitted to the upstream build-process repo, it triggers the build-bots into life, and off they go again....
The Chromium dev community is world-wide, and "on-the-go" ALL the time, 24/7.
I've even built a 'portable' version of UnGoogled Chromium with Widevine built-in for the Puppy Linux community. Despite having all ties cut with Google's proprietary, corporate software, this still works. It's quite popular, too!
Mike.