As the devs don't have their own forum and have delegated everything to Steam, I'm a bit worried about the official support of the DRM-free version.

1. Will they put mods somewhere on their official website or do we have to go to some shady websites?

2. In which specific folders do we have to install them?

3. Will the mod tools be available outside of the steam workshop?

Thanks mate ;)

Is it just me, or are there much more mods available on steam?

There is no doubt that there are more mods available on steam. This is always a risk with any game that has built in support for the steam workshop. This site lists pretty much every mod out there on both steam and TFn and it's clear there about 2x as many mods on steam :

https://www.transportfevermods.com/en/database.html

But there are still literally hundreds of mods on the Transport Fever site including the ones that change the game most significantly and almost all of the best assets, stations, and vehicles.

Makes sense, there are also probably many more players in the Steam Bubble and the game officially promotes Steam Workshop, even ingame I still get the hint to download mods from Steam in the GOG version :)
Thing is, the mods on TransportFever.net can be used with the GOG and Steam version, the Workshop Mods only work with the Steam Client.

I wasn't too worried about buying TF here because it was clear that the modding community was going to be pretty active on TransportFever.net. But in the future I may have to rethink buying games like this here on GOG because not having access to the Steam Workshop can really hurt games like TF that are dependent on user mods for long term playability.

Printer cartridges, capsule coffee, web browsers,... I hope someday soon antitrust enforcement will notice that video games is a billion euro market and put steam in its place.

Or not buy it at all. They now invest another 5000€ into the workshop animating people to use Steam.

Yes, this is very annoying because they could easily just say that they would mirror all contest entries on the .net site. If they get enough content they may put it together as a free DLC like they did with the USA content in Train Fever. But I don't know how many submissions they'll actually get because there doesn't seem to be that much interest in futuristic mods for a game that slows to a crawl by 2020 on any map with more than 8 to 10 cities. Plus 5 weeks isn't much time to come up with, design, model, texture and animate an entirely new vehicle or station.

This is hardly the first time GOG buyers have been ignored by gaming companies but I had hoped for better this time.

Game is on sale right now. Thought about buying it, but then I remembered that most mods are not accessible for us.

Yes there are still more mods on Steam but with over 700 mods currently on www.transportfever.net it's nowhere near as big of a problem as it seemed like it was going to be six or eight months ago.