admgpu experiences a bug where external dispaly goes black coming back from suspend. The build-in display (eDP) does not experience this issue. The workaound is to toggle the external display manually or via scripts. Depending on the compositor used (sway or hyperland). The approach adopted to fix this issue is illustrated below:
Create a script to force the following command (chvt x) to toggle from graphical display back to graphical mode. This is a workaround to get the external display working again. The script is called by systemd in the POST resume operation. The location of the script is /usr/lib/systemd/system-sleep/reset-external-display.sh