Iโm not sure if displays were shipped with the early batches. However, I do know for certain that other developers on the team have successfully displayed stuff on external displays with the L5.
It depends on the type of port your monitor has. You need a USB-C to HDMI adapter cable, USB-C to DisplayPort cable or USB-C to USB-C cable. (Iโm not sure if anyone has tested USB-C to VGA or DVI so far, but that probably works as well.)
See: Frequently Asked Questions ยท Wiki ยท Librem5 / Librem 5 Community Wiki ยท GitLab