Game is being currently sold with a discount on both GOG and Steam. So, I need a piece of advice from people who played it with mods already.

Which version of the game should I purchase, having in mind minimal problems with mod compatibility?

Why do I have this kind of a question? Because I had a bad experience with few other games. When almost all major modding moves to the Steam workshop. And some mods doesn't even have an option to download it for the manual installation in the non-Steam version of the game.

Thanks in advance.

I don´t know about Steam workshop. But I can say, that all major mods are available at nexusmods for manual installation. Also note, that there is no official mod support from the devs atm. It will come with patch 1.8 soon.
In my humble opinion the Gog version is always preferable over Steam.

Good. That's all I had to know. Thanks again.

So, uh, modding.
I need some help with installing mods on gog version. Manual or via BMM -- no luck so far. Has anyone sucsessfully installed mods on your Battletech? If so, what's the trick?

Since patch 1.8 includes ModTek, just place mods in (x):\users\(youruser)\mygames\Battletech\mods

That would be:
(x):\Users\(your user)\AppData\Local\GOG.com\Galaxy\Applications\50593543263669699\Storage\Shared\Files\C0\SGS1

AppData is a hidden folder, either check to show hidden folders or write appdata in path link.

If I'm playing for the first time should I just jump in, or are there some suggested mods to get started with?

I'd recommend to jump in and get a feel for the game first before trying a mod. Also a bit of necro.

So, not going to lie, 2019 is still registering as "last year" to me.

Will try it out without mods before seeing where it goes with it. Great management so far, combat is definitely slower than I expected.

Vanilla is a fine game for me, a bit too easy maybe ... combat is slow, but it is a quite relaxing game ... dont forget, you can press Space Bar to speed up movement or you can toggle this in settings, but for me it looses some feeling. What could be faster for my like is interstellar travel.

Yes! The travel part is the slowest.

Combat is slow in the sense that aside from Mech v. Small Vehicle it has been more a tit for tat exchange. But I am very early in the game so that may change as I get access to better weaponry.

When you get to learn the art of SRM+Laser Vomit you can usually delete 2-3 units easily a turn. Nowhere near as effective as it was but still a simple way to output large amounts of damage in a brawler fight style.

When you get maxed out pilots, Marauders and discover how to abuse called shots well you'll be drowning in salvage.

So, is there any reliable source to download BEX now that nexus download is gone?
Discord only links to links I dont trust and instructions are confusing. Any guide for people not using steam?

I have been on the discord for BEX and the mod owner is working on setting up a github. The best link I found was for one video game site.