SUMMARY
On my system recently recording with spectacle is completely broken, I've tried every format available and all result in a corrupted file.

STEPS TO REPRODUCE
1. Open spectacle and select record region
2. Finish the recording
3. Attempt to play the recorded output, which is a corrupt file.

OBSERVED RESULT
gif and webp will output empty files, mp4 and webm will output really small files that are under 1KB (assuming this is just headers but no data)

EXPECTED RESULT
Videos are output successfully.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  6.17.9-2-cachyos
KDE Plasma Version: 6.5.3
KDE Frameworks Version: 6.20.0
Qt Version: 6.10.1

ADDITIONAL INFORMATION
I noticed this in journal:
Nov 29 21:52:31 camelot spectacle[134701]: VAAPI: VA-API NVDEC driver [direct backend] in use for device "/dev/dri/renderD128"
Nov 29 21:52:57 camelot spectacle[134701]: [libvpx-vp9 @ 0x7f88e4057bc0] v1.15.2
Nov 29 21:52:57 camelot kwin_wayland[1696]: 0x502: GL_INVALID_OPERATION error generated. <image> and <target> are incompatible
Nov 29 21:52:57 camelot kwin_wayland[1696]: Invalid framebuffer status:  "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT"
Nov 29 21:52:57 camelot kwin_wayland[1696]: 0x502: GL_INVALID_OPERATION error generated. <image> and <target> are incompatible
Nov 29 21:52:57 camelot kwin_wayland[1696]: Invalid framebuffer status:  "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT"
Nov 29 21:52:57 camelot kwin_wayland[1696]: 0x502: GL_INVALID_OPERATION error generated. <image> and <target> are incompatible
Nov 29 21:52:57 camelot kwin_wayland[1696]: Invalid framebuffer status:  "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT"
Nov 29 21:52:57 camelot pipewire[1805]: invalid memory type 8
Nov 29 21:52:57 camelot pipewire[1805]: invalid memory type 8
Nov 29 21:52:57 camelot pipewire[1805]: invalid memory type 8
Nov 29 21:52:57 camelot kwin_wayland[1696]: "3342,2466 279x39" Received stream buffer that does not contain user data

The final line will repeat for the entire duration of the recording.