Yes thats pretty much the closest you can get to fully open source today. I have a number of devices I use:
- A Pixel 5 with Graphene because the modern world relies to much on Android Apps, also used as hotspot,
- A Nokia N9 for reading and light browsing, occasional navigation
- A Nokia N900 with Maemo Leste for secure administrative work.
We also have Sailfish devices in the house



There are big differences, Heroic present the gog library in a nice way and supports convenience features like cloud saves (must have with big screen at home and remote gaming on Laptop) as well as gametime tracking, some achievements (dont care about those).
Its far more convenient than Lutris for GoG and of course you can easily backup your Games.