I had same problem. Since I have intel CPU with integrated graphics I went to BIOS settings and enabled that, connected monitor with VGA cable and install worked smoothly, system booting no problem. I tried to switch back to discrete GPU (nvidia 1660s) by installing nvidia drivers, disconnecting iGPU and connecting discrete GPU but was getting black screen with flashing cursor. I was able to alt+f2 to enter terminal, found out that ldm-session-init is crashing lightdm. As temp fix to be able to use system I went to edit xinit and add budgie-desktop so I can just use startx. I use current kernel, tried current and beta nvidia drivers, same crashing lightdm problem.
However, I was fiddling around, uninstalled nvidia drivers and I found out that if I enable "iGPU Multi-Monitor" setting in BIOS (ASUS BIOS Advanced\System Agent Configuration\Graphics Configuration) then everything works no problem without any nvidia drivers while monitor is still connected with discrete GPU and not integrated one. After many days I finally booted into system like normal human, went to install nvidia drivers from doflicky and rebooted. All worked fine, went to BIOS to disable iGPU Multi-Monitor and one reboot after I can still boot into solus, all works smooth. I have no idea whats going on..