Very simple steel bumper with welded d-rings welded. I replaced my Rubicon's plastic bumper and opted to go without spare because I previously installed AAL's Spare Tire Delete Kit.
The bumper came bare metal so I spray painted starting with (1) Rust-oleum Self Etching Primer and (2) Rust-oleum Textured Black. Before you start painting, make sure to use fine sanding paper or a scuff pad to create a better bond. Also use some type of mild cleaner to remove any particles from the surface.
Bought the bumper from Motobilt because they offer veteran discount via GovX verification https://motobilt.com/products/jeep-jl-rear-bumper-crusher-no-spare-2018-present-wrangler-jl
Canopus - 3M Scotch Brite Scuff Pads Very Fine and Ultra Fine https://www.amazon.com/gp/product/B075VCCZW9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Rust-Oleum Stops Rust Flat Gray Spray Primer https://www.lowes.com/pd/Rust-Oleum-Stops-Rust-Flat-Gray-Spray-Primer-Actual-Net-Contents-12-oz/3728805
Rust-Oleum Textured Black Spray Paint https://www.homedepot.com/p/Rust-Oleum-Stops-Rust-12-oz-Textured-Black-Protective-Spray-Paint-7220830/100121155