Yeah, I'm on Linux too, and you're right that GOG isn't as convenient as Steam on Linux, but you don't have to mess around with bottles to get them working. Heroic Games Launcher is excellent and has Wine and Proton built in, so installing GOG games and playing them through that is almost as convenient as playing through Steam on Linux.

I find that compared to Steam, I have to tinker slightly more often than Steam to get them working; otherwise, most games install and play perfectly just like on Steam. There's an official GOG client called GOG Galaxy, but it's only on Windows and Mac, so third-party launchers like Heroic are the best options on Linux. Plus, somewhat recently GOG officially partnered with Heroic Games Launcher which improved the compatibility quite a bit. There's no achievement support in Heroic yet, but they are working on the feature for it, as far as I'm aware.

I can't remember where the option is, but you can also add the GOG games from your library in Heroic to Steam as a non-steam game.

As for sales, like I was saying before, the sales across GOG and Steam seem to be very similar to each other, having the same price cuts at the same time as each other.

One thing to be weary of when buying games from GOG on Linux is when you buy games that are playable online, such as No Man's Sky and Divinity: Original Sin II. These games rely on GOG Galaxy to connect you online, which currently isn't functional on Heroic Launcher (but may get support in the future). One other thing to note is that occasionally I've noticed that a game publisher releases an official Linux port on Steam, but ignores it on GOG. I was disappointment when this happened to me. I bought the whole Metro series in a bundle from GOG, but I only found out afterwards, that on Steam their are actually official Linux ports for the whole trilogy. I use ProtonDB to quickly check which Steam games have Linux ports