Raspberry Pi doesn't boot without a monitor after normal install

Hi everyone,

I’ve had an installation of Manjaro KDE on my Raspberry Pi 4 8GB. It booted to a GUI when connected to a montor and booted with SSH available if no monitor was connected.
Long story short a necessity to reinstall the system came along…

I’ve changed the bootloader to boot from USB SSD using the Raspberry Pi Imager and installed Manjaro with a monitor, keyboard and mouse.
However now I want to be able to use it in this hybrid way. But after booting without a monitor connected - the rpi is not accessible through SSH (the IP is static for it)

Does anyone have any thoughts on this?

When you set it up with the gui, did you enable ssh before shutting down, disconnecting the monitor, and then attempting to login via ssh?

Verify on another computer that in the /boot/cmdline.txt the PARTUUID= value actually matches what it is.