DRM-options not available in Firefox on Pi 5

[nameiwillforget]

I'd like to replace the cable subscription of my father that he uses to watch Netflix over with a Raspberry Pi 5 he can use to watch through Firefox, on which I installed Gentoo arm64. But when I use Firefox to access a Netflix video, I get an error message that tells me playing the video is impossible. I get the same error message when I try this on my desktop, but there, FF provides an option to enable DRM-protected content, which does not appear on the PI5 FF. I found https://wiki.gentoo.org/wiki/Streaming_DRM_protected_content and looked at the steps there, but when I go into the FF settings, I can't find the option to enable DRM. I tried to emerge firefox-bin knowing that it would fail, to see what would happen, and it gave me an error message that CONFIG_SECCOMP was not set and playing DRM-protected content would be impossible, so I emerged genkernel to look at the kernel config, but found that CONFIG_SECCOMP was set. I have a theory though: while installing most packages I overlooked that the symlink to the Raspberry Pi kernel, which I had emerged during the system setup, was not set, so portage must have used the running kernel, but I did the system configuration through a QEMU setup, so I'm assuming it used the kernel of the host? Which would have been the standard amd64 Gentoo kernel, which I'm sure has seccomp enabled as well, but maybe there was some mixup? In any case, I tried re-emerging FF on the Pi5 itself, with the symlink to the kernel set, and I did not get any error messages, or complaints about seccomp, but the option to enable DRM is still not in the FF settings. So I'm running out of guesses. Maybe some package that FF depends on was compiled thinking that seccomp was unset? But how can I find out which one, or should I just recompile everything?

[nameiwillforget]

So, I've re-compiled every program I had on my Pi and the option to enable DRM content is still not in the settings of Firefox, but I also got no error when I re-emerged it. I'm running out of ideas. I can install Chromium, but that's about all I can think of.

Maybe there is some group my family user should be in to run DRM? I'll try to start FF as root to see.

Edit: I just found this: https://discussion.fedoraproject.org/t/firefox-and-widevine-aarch64-support/86797

Might that be the same problem as in my situation?

Edit2: I've looked into emerging Chromium or Vivaldi but in both cases the '(-widevine)'USE flag is bracketed out.

[M95D]

[nameiwillforget]

FF was compiled with gmp-autoupdate, but not with openh264. I've re-compiled it with openh264, but the problem persists. The configure options are

[Hu]

/proc/config.gz is an optional, but highly recommended, kernel feature, gated behind CONFIG_IKCONFIG_PROC. If you don't have it, you can also supply the .config that was used to build the kernel.