Widevine
Introduction
Widevine is a proprietary DRM system, used to secure media content. It is needed to use various video and audio streaming services (ie. Netflix or Spotify).
Running it on Linux and/or ARM devices is possible, however it requires the Linux system to be based on glibc library, which Alpine and PostmarketOS does not use.
Installation
Alpine Linux lists multiple ways to run glibc programs. Take a look, if you're hoping to find a more comfortable workaround.
Using Distrobox workaround
Distrobox is a good way to run glibc-dependent software. Choose a glibc-based distribution (most of the well known ones will be fine) and see Alpine Linux wiki for instructions.
Example using a Fedora container and Asahi Linux' Widevine Installer:
distrobox create --image fedora --name your_container_name sudo dnf install firefox widevine-installer sudo widevine-installer exit distrobox enter your_container_name -- /usr/bin/bash -l -c firefox
Keep in mind that you will need to set a user agent string of a Chrome+Chromebook device to make ARM Linux Widevine binary work.
For convenience, you may want to add the last command to a .desktop file in ~/.local/share/applications/