Yeah so turns out Niche can be modded after all, we just needed a universal mod loader that works for all unity games.
Here's what you must do to get Niche ready for modding and also the link to the MelonLoader Wiki
REQUIREMENTS
.Net Framework 4.8 Runtime (or higher)
Microsoft Visual Studio
You can either install manually or automatically, I'll write about the latter since that's the one i know how to do
Download MelonLoader.Installer.exe
Run the installer
select the niche app file found in This PC/C:/Programs/Steam/Steamapps/Common/Niche/Windows/either 32bit or 64bit depending on which version you have installed
Select the 0.5.7 version (higher versions dont work)
(Should look like this)
Install!
Launch Niche to check if MelonLoader has installed correctly
If it has, a console should appear at startup
If the console doesn't appear, try to install MelonLoader in the other Bit folder
There are currently no mods made specifically for Niche, but there are some universal mods you can add instead! Like the Unity Explorer which lets you delete or add things :DD
Get the MonoMelonLoader versions and copy-paste the .dll files into the mod folder that should have appeared in whichever 'bit folder you installed the loader in. Check if your antivirus has taken the .dll files in quarantine and release them if so
That should be all, tell me if you have problems!