I did a video tutorial and demonstration showing the Steam, FEX Emulator, and Distrobox setup I documented on the postmarketOS wiki here:

https://wiki.postmarketos.org/wiki/Steam

I go through the setup process for the Ubuntu container, FEX emulator, Steam, and then install and test two games - Half Life 2: Lost Coast and Tomb Raider (2013) to demonstrate gaming performance on an ARM device (in this case a Xiaomi Pad 5 Pro with Qualcomm Snapdragon 870 chip).