Doesn't FreeBSD provide Linux kernel ABI compatibility?

The linux community took a little bit but was able to get the DRM stuff working through wine (I think it was firefox+silvervine or something)and I think they now have a native solution. I doubt there's any real reason you couldn't get it working, it's just the FreeBSD community is a lot smaller and you'll have to convince somebody to work on it unless you have the know-how to yourself.

Yes. It's getting somewhat out of date though (e.g. current versions of Steam can't connect to the network)

Out of curiosity: is it that FreeBSD has the old socketcall(2) but not the newer fine-grained system calls?

Possibly. I don't remember what it was, maybe it was actually some new arguments or something

How do you hack around it?

By getting media from "alternative" DRM free sources.

I've acquired media from "the usual places" for which I own the physical disc because it's easier and faster than handbraking it myself.

Your only options are to videos from a DRM free source or remove the DRM. The later is prohibited in most jurisdictions. Just hope your vision and hearing stay unimpaired because DRM locks out all accessibility software.

a VM maybe?