dtgreene: Are you saying that Heroic Games Launcher *doesn't* allow you to install from the offline installers?
Ranayna: I have to admit that i did not try. But at first glance there does not seem to be a way.
I think you're correct, there's no such option in Heroic.
Thanks, dtgreene, for the question and thanks to all for your answers. I'm still looking for the best solution for myself, so I find this thread really useful.
My current choice is:
Linux Mint + Cinnamon + Playonlinux + Steam For the distro - I had a lot of fun with distro hopping, but at some point I've become lazy (or just not enough time to experiment) and I decided to take something polished, well-supported and working out-of-the-box. I don't understand Wine and its prefixes, so I'm using Playonlinux as a convenient wrapper - it allows me to create separate/sandboxed Wine environments, choose Wine version, add dlls/libraries, use some additional options etc.
I've tried Heroic launcher recently and:
* it magically made all my Epic freebies playable out of the box :O, so I love it,
* it cannot use offline installers, so I cannot use it with my GOG account, because I don't want to log in here (because I don't want time tracking etc.), so it will never be my first choice,
* it's super simple and gives some crucial options, including multiple Wine and Proton versions, which is great.
After reading all the opinions I think I'll try Lutris. It looks it may replace POL for me.