@shmu26
I found this in some other place. You need to start and enable the services.
Edit: This comes from the Hylafax page.
It has it’s own systemd startup configurations.
systemctl enable hylafax-hfaxd
systemctl enable hylafax-faxq
systemctl start hylafax-hfaxd
systemctl start hylafax-faxq
Edit: Hopefully this works!
@shmu26
Were these the proper commands to get Hylafax to start on boot?
They didn’t work for me. Maybe they work for a different version of hylafax.
Check the file
/etc/default/hylafax
Make sure the line is uncommented
run hylafax=1
I got that from here:
That file does not exist on my system.
I’m not sure how you originally started Hylafax so it worked. But according to the wiki you have to enable it something like this systemctl enable faxgetty@ttyACM0.service.
Then i assumed you would start the other services that start the fax service on boot which i gave you. I’m no expert on this. I understand you have it working in a way that makes it usable but not starting the fax on boot.
It’s hard to decipher the Arch wiki. 
Don’t sweat over it. No big deal to run “sudo hylafax start” once in a while.
I am just thankful this dinosaur works at all. I tried installing it on Ubuntu and it failed miserably.