On a cloud provider like Vultr you have access to the console. It would be nice if that was a big screen.
Right now, with the splash screen disabled, Grub provides a high-res boot, and then after boot it drops to 80x24.
Any hints?
Self-answer: add "vga=791" "nomodeset" to the boot.kernelParams array 
I created kernel.nix: boot.vesa implies nomodeset by wmertens · Pull Request #63090 · NixOS/nixpkgs · GitHub to make this the default with boot.vesa = true