Allow g-sync compatible option no longer visible

[pianoplanepete]

Classic "was working, no longer working, asking for help might be faster than persevering" post.
I have a gsync compatible GPU (possibly important: I have two), compatible monitor, (with freesync enabled) and I have the latest nvidia-drivers installed.
I use KDE with X11.
I use heroic games launcher to play games. I recently upgraded my hardware (amd gpu to nvidia gpu) and I have been playing with a lot of settings, as one does.
I think that the G-sync options in the nvidia-settings weren't visible out of the box. After playing with some settings (no clue which ones) it was. Then I played with settings some more and the g-sync option has been gone since. I thought all I changed was install gamescope, but after removing it the g-sync setting did not return. I tried an older version of nvidia-drivers but no luck. I use nvidia-xconfig to populate xorg.conf. Relevant lines:

VertRefresh 48.0 - 144.0
Option "metamodes" "3440x1440_144 +0+0 {AllowGSYNCCompatible=On}"

I have g-sync enabled in the advanced settings of nvidia-settings, and on the display adapter page it is indicated as enabled. Flipping works in games, but as the indicator option is missing, I can't be sure gsync is working. I don't see g-sync errors in dmesg. I am getting an error when running nvidia-settings from the terminal (see below).

I installed a fresh copy of Gentoo (again with KDE, nvidia-drivers, and using binary packages, including the kernel), but again no G-Sync option in the OpenGL page of nvidia-settings. So now I have two environments on separate disks and gsync is not working on either. The new environment is very vanilla with no game specific packages installed.
Things I can still check (but troubleshooting exhaustion is kicking in):
- use a custom kernel
- use only one GPU
- older version of plasma
- MTRR?
- figure out if the following error is relevant: (nvidia-settings:23075): GLib-GObject-CRITICAL **: 09:28:22.998: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
- gamemode (have it installed on the old environment, but not on the new environment)
- different displayport cable or slot
- BIOS settings

Adaptive sync on Wayland seems to be working, but I get micro stutter in games.