Hey there folks!
I have an HP Elitedesk 705 with a Ryzen 3400G. I was gaming previously with CachyOS on an i5-8500T and figured the vega gpu would be a little bit quicker for the old and indie games I like. Unfortunately, I can only get into the installation with the legacy no graphics mode, “nomodeset” is what I think it is called? But I’m not sure how to turn on the mesa driver after installing that way. If I use the normal or LTS installer I get a black screen about half way into the initialization.
So far I’ve tried using all three different DisplayPorts. I’m ordering a DP → HDMI because I’ve heard that can help with black screens. I’ve tried a few different LLM suggested command line booting options:
amdgpu.dc=0
amdgpu.aspm=0
a few others.
Nothing works as of yet. I run into the same issue with Bazzite. I think I’m going to try Ubuntu 26.04 next, but not looking forward to figuring out proton/steam/wine/etc… Cachy makes that so easy!
I’ve got the same 705 G5 and I don’t have any issues. I’m plugged straight into DP not HDMI. I boot off the normal kernel not LTS.
Once you’ve got it installed. I’ve found switching to ZSwap and running the Cachy SLR proton provides some improvements.
Will give it a shot! I know you said you got it working with the DP, so that’s cool, what kind of monitor? I also ordered the HDMI flexio to see if that helps. Will keep trying to get it to boot via the normal method.
So it worked with the FlexIO HDMI adapter: HP HDMI Port Flex IO (705)
Same exact cachyos ISO, now no eternal blank screen, booted into the launcher.
Not sure If we’ll get to the bottom of my DP issue now that I’ve found a work around. But happy I’m able to use cachyos again. Hopefully someone else (or an LLM) finds this and helps somebody else!
Didn’t last long! After a successful install at glorious 1080p and 100Hz, amdgpu failed to load on first boot 
After some troubleshooting it was suggested that i add:
options amdgpu dc=0
to
/etc/modprobe.d/amdgpu.conf
That seemed to do the trick, now running in 1080p 100 again!
So that setting did not fix the issue! The saga continues.
It reverted to the software driver again. This time I poked around the BIOS some more and found CSM buried in the boot mode and it was turned on/legacy mode. I turned it off and went full UEFI mode and the agesa driver booted right away no issues.
