I understand that without a monitor connected, OpenGL doesn't work on the Pi. Chromium and OpenCPN need these to perform at all well. Unfortunately, OpenCPN seems to forget the setting to disable OpenGL so that isn't great.
A good solution that works for me is to add the statement video=HDMI-A-1:1920x1080@60D to the end of the file cmdline.txt
Let me know if it works for you.
A good solution that works for me is to add the statement video=HDMI-A-1:1920x1080@60D to the end of the file cmdline.txt
Let me know if it works for you.