Just tried it with a USB drive connected and mounted in /etc/fstab. Still works. ¯\_(ツ)_/¯
Same as previous post, but with a USB 3.0 card reader connected, with a 32GB FAT32 formatted card inside.
Connecting from, Win10 laptop using WSL for SSH.
~$ ssh pi@raspberrypi
Linux raspberrypi 4.19.57-v7l+ #1244 SMP Thu Jul 4 18:48:07 BST 2019 armv7l
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Fri Aug 23 22:24:29 2019 from 192.168.2.10
pi@raspberrypi:~ $ ls /mnt/sda1
'System Volume Information'
pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.19.57-v7l+ #1244 SMP Thu Jul 4 18:48:07 BST 2019 armv7l GNU/Linux
pi@raspberrypi:~ $ cat /etc/fstab
proc /proc proc defaults 0 0
PARTUUID=84b22cec-01 /boot vfat defaults 0 2
PARTUUID=84b22cec-02 / ext4 defaults,noatime 0 1
/dev/sda1 /mnt/sda1 vfat defaults 0 0
OP indicated the issue was mounting a USB drive at boot (not failure to boot), but I still don't understand how connecting an HDMI monitor could affect mounting (and I can't replicate the problem).
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?