First of all, I don't want to hear about try this, try that, edit this and that, I have done it all, so now my warning. Do not use TV headless on Ubuntu Bionic, it just doesn't work, there's a lot of people complaining about trying to add the machine to a TV account and fails with some sort of connection problem, or other errors relating to initiating the login sequence during headless setup using 'teamviewer setup' as root, and the problem still hasn't been fixed in version 14, the bug was reported way back from V11. I tried everything possible from putting the server on the DMZ zone via the router, to purging TV and re-installing it, to even manually adding the machine to my TV account using 'teamviewer info' and copying the ID and using the password setup using 'teamviewer passwd' but the client says my server is offline, but everything else works fine, I can use telnet SSH, I can use VNC, I can access apache web server, but TV just will not work. I'll keep an eye on the progression of the bug, but in the mean time I have purged TV and using VNC for now.
Re: Warning about using headless TV on Ubuntu Bionic
I'm having a similar experience. What I have found is a monitor must be connected when the machine is booted to be able to connect via TV. The monitor can then be disconnected. This situation is a disaster if you need to restart the box. SSH works fine. TV needs to get cracking on this.