Particle System - Project objects not visible in the 'Select Mesh' window under 'Renderer'

I've been searching a lot about this but I didn't find anyone who has the same problem. I want to make a particle system which emits mesh particles, but the only meshes available are Cube, Capsule, Cylinder, Plane, Sphere and Quad under the Assets 'Tab' in the 'Select Mesh' pop-up window, and 'None' in 'Scene'.

I have ProBuilder installed on the project, does that have something to do with this?