Blank window on startup unless --disable-gpu is specified

[shoop]

I just switched to Fedora Silverblue 35 and want to avoid installing software on the host OS if possible.

Running this flatpak resulted in a blank window frame with a correct title but only grey contents.
As my main desktop is GNOME on Wayland, I tried the instructions in PR #229 which kind-of worked but as stated there, this disables the window frame so I have only the correct contents without any way to maximize etc.
Google was of no help but by accident I stumbled upon the --disable-gpu flag, and it turns out that this fixes my problem.

GPU info for this machine:

$ lspci  -v -s  $(lspci | grep ' VGA ' | cut -d" " -f 1)
01:00.0 VGA compatible controller: NVIDIA Corporation GM200 [GeForce GTX 980 Ti] (rev a1) (prog-if 00 [VGA controller])
	Subsystem: ASUSTeK Computer Inc. Device 8548
	Flags: bus master, fast devsel, latency 0, IRQ 134
	Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
	Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Memory at f0000000 (64-bit, prefetchable) [size=32M]
	I/O ports at e000 [size=128]
	Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: nouveau
	Kernel modules: nouveau

Most notably I'm not using the proprietary nvidia driver:

$ lsmod | grep '^drm'
drm_kms_helper        311296  1 nouveau
drm_ttm_helper         16384  1 nouveau
drm                   630784  12 drm_kms_helper,drm_ttm_helper,ttm,nouveau

Would like to understand if the flag can be dropped in some way.