Hardware acceleration with VA-API can't find the right drivers

I am using Debian Sid, kernel 5.19.0-1-amd64. My machine is a ThinkPad T14 Gen 3 with an integrated graphics controller and an NVIDIA GPU; here is the result of lshw -c display:

*-display                 
       description: VGA compatible controller
       product: Alder Lake-P Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       logical name: /dev/fb0
       version: 0c
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom fb
       configuration: depth=32 driver=i915 latency=0 mode=3840x2160 resolution=3840,2400 visual=truecolor xres=3840 yres=2160
       resources: iomemory:600-5ff iomemory:400-3ff irq:178 memory:6052000000-6052ffffff memory:4000000000-400fffffff ioport:3000(size=64) memory:c0000-dffff memory:4010000000-4016ffffff memory:4020000000-40ffffffff
  *-display
       description: 3D controller
       product: TU117M [GeForce MX550]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       version: a1
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list rom
       configuration: driver=nvidia latency=0
       resources: iomemory:600-5ff iomemory:600-5ff irq:176 memory:bd000000-bdffffff memory:6040000000-604fffffff memory:6050000000-6051ffffff ioport:2000(size=128)

I'm trying to get hardware acceleration to work (mostly within Chrome, so Google Meet & Zoom Web run smoothly). The problem seems to be that VA-API (version 1.15.0) doesn't seem to be connecting to either card, regardless of what environment parameter I use.

root@cyclone:/# vainfo
libva info: VA-API version 1.15.0
libva error: vaGetDriverNameByIndex() failed with unknown libva error, driver_name = (null)
vaInitialize failed with error code -1 (unknown libva error),exit

root@cyclone:/# LIBVA_DRIVER_NAME=iHD vainfo
libva info: VA-API version 1.15.0
libva info: User environment variable requested driver 'iHD'
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_15
DRM_IOCTL_I915_GEM_APERTURE failed: Invalid argument
Assuming 131072kB available aperture size.
May lead to reduced performance or incorrect rendering.
get chip id failed: -1 
param: 4, val: 0
libva error: /usr/lib/x86_64-linux-gnu/dri/iHD_drv_video.so init failed
libva info: va_openDriver() returns 18
vaInitialize failed with error code 18 (invalid parameter),exit

root@cyclone:/# LIBVA_DRIVER_NAME=nvidia vainfo
libva info: VA-API version 1.15.0
libva info: User environment variable requested driver 'nvidia'
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/nvidia_drv_video.so
libva info: Found init function __vaDriverInit_1_0
libva error: /usr/lib/x86_64-linux-gnu/dri/nvidia_drv_video.so init failed
libva info: va_openDriver() returns 1
vaInitialize failed with error code 1 (operation failed),exit

The problem is the same regardless of whether I install the free driver for the Intel hardware (package intel-media-va-driver) or the non-free one (intel-media-va-driver-non-free). For NVIDIA drivers, I have tried installing the package recommended by nvidia-detect (which was simply nvidia-driver) as well as the other suggested one (nvidia-testla-470-driver), both of them fail in the same way. I also tried to modify Xorg config to [only use the NVIDIA GPU](https://wiki.archlinux.org/title/NVIDIA_Optimus#Use_NVIDIA_graphics_only) , but this did not change anything. I don't know if it's related, but intel_gpu_top seems to fail with an obscure error message as well:

root@cyclone:/# intel_gpu_top
intel_gpu_top: ../tools/intel_gpu_top.c:1910: init_engine_classes: Assertion `max >= 0' failed.
Aborted

What should my next steps be here?