Can you please add the following clients please:

Twitch, BattleNet and BethesdaNet

Second and third are already implemented. Search this forum for links.

Twitch also got a community integration few days ago: https://github.com/nyash-qq/galaxy-plugin-twitch
Though games will be listed as 'Amazon' because people at GOG didn't yet add Twitch as a possible platform. They know though and will add it.
I also hope they'll add icons for Twitch and Humble Bundle, mainly for the looks but also because I got some games on both and can't tell them apart without clicking on them.

Just click on 'clone or download', download it as zip, extract the zip and copy the folder into galaxys plugin folder (the one in AppData is recommended I guess, but the one inside the galaxy program folder also works). Restart the client and connect the integration.

I tried in both folders and it didnt work for me. I was able to get one made for GW2 to work but not the twitch one.

At which point exactly do you encounter problems with the twitch plugin ?

Get the release from here instead: https://github.com/nyash-qq/galaxy-plugin-twitch/releases

Do you think Humble Store integration is possible? I mean just for games you own DRM-free through it. There's no point in stuff like Steam keys you bought there showing up because you already will see those on the platform they activated on.

Side note if you're looking to buy an indie game on GoG or Steam take a look at Humble because sometimes you'll get a Steam key *and* a DRM-free copy.

There actually is a Humble Store integration: https://github.com/UncleGoogle/galaxy-integration-humblebundle