HDMI external monitor not working [Linux Lite 4.2]

[lite noob]

Kernel: 4.15.0-38-generic x86_64
Hardware: Dell latitude 7270
OS: Linux Lite 4.2

I've had this problem with my current distro of Linux Lite 4.2 and with a prior distro of Linux Mint 18.3 Sylvia. When I connect my HDMI cable to my TV, it's not detected by the computer. Then I learned that you have to boot with the HDMI cable already plugged in. I do see the DELL logo while in the POST, but after that the image on the TV fades and it goes back to my laptop and shows me the log in screen. After logging in, the computer doesn't detect the TV. I'm even able to see GRUB on the TV if I access it. But when it tries to load the Linux OS, the image switches from displaying on the TV to the laptop screen.

Also tried booting from other live distros, with no luck.

I've read on other forums that I have to switch between some nVidia video drivers, but I don't think that applies to my configuration because my video card is from Intel, and the BIOS has no video settings I can play with to switch drivers.

On [url=http://"https://askubuntu.com/questions/927639/external-monitor-hdmi-does-not-work-with-intel-hd5500-ubuntu-16-04"]this thread[/url] it was suggested to update to kernel 4.15.18-041518-generic, which didn't work for me.

Code:

$sudo lshw -c video

  *-display                 
       description: VGA compatible controller
       product: HD Graphics 520
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:128 memory:e0000000-e0ffffff memory:d0000000-dfffffff ioport:f000(size=64) memory:c0000-dffff

Code:

$xrandar

Screen 0: minimum 320 x 200, current 1366 x 768, maximum 8192 x 8192
eDP-1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 277mm x 156mm
   1366x768      60.00*+  47.49 
   1360x768      59.80    59.96 
   1280x720      60.00    59.99    59.86    59.74 
   1024x768      60.04    60.00 
   960x720       60.00 
   928x696       60.05 
   896x672       60.01 
   1024x576      59.95    59.96    59.90    59.82 
   960x600       59.93    60.00 
   960x540       59.96    59.99    59.63    59.82 
   800x600       60.00    60.32    56.25 
   840x525       60.01    59.88 
   864x486       59.92    59.57 
   800x512       60.17 
   700x525       59.98 
   800x450       59.95    59.82 
   640x512       60.02 
   720x450       59.89 
   700x450       59.96    59.88 
   640x480       60.00    59.94 
   720x405       59.51    58.99 
   684x384       59.88    59.85 
   680x384       59.80    59.96 
   640x400       59.88    59.98 
   576x432       60.06 
   640x360       59.86    59.83    59.84    59.32 
   512x384       60.00 
   512x288       60.00    59.92 
   480x270       59.63    59.82 
   400x300       60.32    56.34 
   432x243       59.92    59.57 
   320x240       60.05 
   360x202       59.51    59.13 
   320x180       59.84    59.32 
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)

Code:

$lspci -k -s 00:02.0

00:02.0 VGA compatible controller: Intel Corporation HD Graphics 520 (rev 07)
   Subsystem: Dell Skylake GT2 [HD Graphics 520]
   Kernel driver in use: i915
   Kernel modules: i915

Question #1: How can I get the external HDMI port to work?

Question #2: Is it true that you HAVE to connect the HDMI cable to your computer BEFORE booting the Linux distro?

Thanks