Name: Hydrapaper
Project page: https://gitlab.com/gabmus/HydraPaper
Function: Allows the user to set two different wallpapers for different monitors. Supports Budgie, GNOME 3, and MATE. The only alternative I found on the Solus repository is a package called "Nitrogen" which didn't work for me.
Open source? Yes.
Releases: https://gitlab.com/gabmus/HydraPaper/-/releases
Latest release zip file: https://gitlab.com/gabmus/HydraPaper/-/archive/1.4.2/HydraPaper-1.4.2.zip
Repository: https://gitlab.com/gabmus/HydraPaper/tree/master
Note: Hydrapaper is available on Flatpak (flathub org.gabmus.hydrapaper) and works for me in Solus OS. I think its a good suggestion for the eopkg Solus repository.