Fedora 40 KDE spin running updates-testing. 99% of the time I'm in Konsole, browsers (Fedora, Edge and Chromium) and VS Code.  My system does not hibernate or sleep. The only thing I do is set the monitors to turn off. I have a 2nd system plugged into the DP ports of the monitors also running Fedora 40 KDE spin running updates-testing and I haven't noticed the issue there (but I only really use that for Steam gaming, so don't have enough windows open to really test it), so I think it's specific to the "HDMI" handling code.

The monitors do sleep now in KDE 6 (thanks devs), but when waking from monitor "off" the Konsole windows and browsers windows tend to be all over, but in repeatable fashion. I tend to have 1 screen with 1/2 Konsole (left side) and then 2 1/4 Konsole windows (right top and bottom) and the 1/2 window tends to shrink to 1/4 and then go halfway off the top left of the screen in the same spot every time. On other virtual desktops the windows will go full screen or move to the other side. The firefox browser sometimes moves completely off screen to the right or goes full screen (it's usually 1/2 screen) and the Edge instance tends to move left to the other monitor. I don't have "scientific" data, but my gut is that the "math" calculating Window positions on-wake is wrong and/or what it's using to "ID" the monitors is wrong and it gets confused. The fact it's also resizing windows is odd.

note: KDE used to (pre-6.x) identify the monitors with the same "ID", but they appear to ID differently now.

Nothing is crashing and everything "works". I just have to move my windows back to where I want them every time the monitors sleep. It would be nice to not do that. This has been happening to me since KDE6 launch (i started with F40 beta as soon as it dropped).

monitors: 2 x Dell U2719D via HDMI

Operating System: Fedora Linux 40
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.0
Kernel Version: 6.8.10-300.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × Intel® Core™ i7-8700 CPU @ 3.20GHz
Memory: 31.1 GiB of RAM
Graphics Processor: AMD Radeon RX 550 / 550 Series
Manufacturer: Dell Inc.
Product Name: OptiPlex 7060