For those who shoot 4x5 (or larger), it's reasonably simple to use a view camera as an enlarger. In a weekend, I built a mount to hold a negative and a light in place of the usual graflok back. Primary materials were laser-cut wood, RGB LED strips, and diffusion paper. I built an Arduino-based controller for use as a variable contrast timer (changing the blue/green mix on the LED strips when printing). The whole rig was about the cost of a good set of contrast filters and took 15 hours of my time.

The back holds the negative on the camera, which I put on an old aluminum tripod and point straight down in a blacked-out bathroom. I develop through a 150mm Nikkor W 4x5 lens; held open. Since I use the timer for timing and never touch the camera/enlarger while exposing the print, the setup is rock-solid and vibration-free.