Confirmed also on an HP ProBook 450 G1, for netinst.so installation via either USB or CD, and on both Jessie stable (8.8) and Stretch RC4.
[BTW please pardon my responding via email: I struggled with the reportbug program 3 times and finally gave up, reportbug itself is just too buggy! :-( :-( .. I am attaching 3 screenshots to this email: Hope they make it through. Please let me know if I can help by providing any additional information. I am guessing it is just some funkiness with an unsupported chip on this laptop series.]
* What led up to the situation?
Attempt to install via either USB- or CD- based netinst.iso (tried Jessie 8.8 stable and Stretch RC4. Screenshots are from RC4)
As with the OP (Bengt), first screen looks fine (as you can see in screenshot) but subsequent screen (whether graphical mode or text mode) is garbled.
* What exactly did you do (or not do) that was effective (or ineffective)?
I tried going to the Advanced Options menu and putting in various versions of the video (video=, vga=) boot parameter to change the video mode (which appears to be the problem: perhaps the hardware on this laptop has only limited modes it can display, or perhaps its chip has limited linux support, etc.) But nothing I tried worked (vga=788, vga=791, etc.)
I don't remember all the modes I tried, but I tried everything reasonable (or so I thought), and VESA standard (e.g., 640x480, 800x600, 1024x768, etc.) as well as even an additional one I tried, calculated for the laptop's native highest resolution mode (1366x768).
* What was the outcome of this action?
Just garbled screens. Nothing changes regardless of video mode
* What outcome did you expect instead?
Non-garbled, readable screen.
What is frustrating-tantalizing is that obviously the installer *can* find at least one video mode that works, because the first screen does syn (as seen in first image/screenshot). (Maybe this is a 640x480 mode I missed or something.)
