I. "I can’t see the mod in the launcher/ the launcher does not detect the mod issue"

In this case you need to follow this instruction, such situation happens when you are subscribing several large mods. It seems like launcher is messing up proper detection of IDs.
1. Quit HOI4 and HOI4 (Paradox) Launcher
2. Unsubscribe from all mods. HOI4 Workshop -> Your files (under your avatar) -> Subscribed items - > Unsubscribe From All .
3. Quit Steam
4. Go to SteamLibrary\steamapps\workshop\content\394360 and delete everything.
5. Go to (C:\Users%username%)Documents\Paradox Interactive\Hearts of Iron IV and delete the following files:
-dlc_load.json
-game_data.json
-launcher-v2.sqlite
-mods_registry.json (if present)
-delete "mod" folder (if present)
-everything inside last_mods={ } in settings.txt (if present)
6.Restart Steam.
7. Open Paradox launcher.
8. Close Paradox launcher.
9. Resubscribe to your mods.
10. WAIT UNTIL ALL DOWNLOADS ARE DONE. DO NOT START PARADOX LAUNCHER UNTIL DOWNLOADS ARE COMPLETE.
11. Start Paradox Launcher.

Remember to save your previously subscribed mods

II. "Does this mod work on Linux system?"

No, it does not and for the moment being we have no idea how to make it work. At least for now.

III. Water in my game looks weird, what happened?

If you approach such issue, you should download and start using non-reflective mod. It will fix the problem.
https://cdn.discordapp.com/attachments/899279201197228034/909116413686472774/unknown.png

IV. Hey, why the interface looks strange? Why can't I see stuff, what the heck?!

The reason is that the current GUI we are using, and which was fixed for NSB hotfix update seems to not be compatible with all kinds of resolutions. You just need to change it to 1920:1080 and things will look fine.
https://cdn.discordapp.com/attachments/899279201197228034/993223006224666664/unknown.png

V. Oh no, why is toolpack not working reeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee!!!

It is working, just not every version of it since we changed GUI to our own in the mod. Here is a version which works with our mod.
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=1367081844

VI. Large peace-conferences are crushing the game!

Yeah, if you happen to have a weak PC! (Like me for example :FrogWorrySad:)
There is however a solution to this, namely the player lead conferences should allow you to save a lot of your PC processing power and thus preventing the game from crushing.
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=846066944