I also had this problem two months ago when installing Trisquel 8 in my Acer
laptop with an old Radeon card (AMD/ATI Park Mobility Radeon HD 5470)
However -after different trials- I was able to solve the problem as follows:
- After installing Trisquel 8 the Vesa driver was only giving a 1280x720
resolution and it could not handle an external monitor
- I updated Trisquel using the software updater and the resolution was still
the same
- Then, in order to be able to use the radeon driver, I updated the kernel to
the HWE-kernel available in the Trisquel repositories:
$ sudo apt install --install-recommends linux-generic-hwe-8.0
xserver-xorg-hwe-16.04
$ sudo update-grub
- I restarted my laptop
- Finally, I added the line "modprobe radeon" at the end of my /etc/rc.local
file to make sure the kernel loads the radeon driver when I start Trisquel
Everything works fine now: I am getting a 1366x768 resolution in the laptop
display and I can use it together with a 24" external monitor.
Hope this comment helps other people having a similar problem!
