It's FOSS - https://itsfoss.com/ubo-icon-theme/
Brief: If you want to give your Linux desktop a real vintage look, try Ubo icon theme. This hand drawn icon theme will make your Linux desktop look like Flintstones’ computer.
Legend has it that Ubo Icons were created with a ballpoint pen and then colorized in our very own GIMP. A ballpoint pen, mind you. Ubo Icon pack does add a unique twist to your desktop. For someone looking for a rather ragged look on your Linux desktop, Ubo icon pack is a must-have. A vintage looking wallpaper plus Ubo Icons and you have it, a desktop like none other.