Intel QuickSync transcoding with Jellyfin

My server running OpenMediaVault 6 has an Intel Celeron J4105 CPU which should be capable of handling a 4k transcode. Jellyfin runs in a docker container which I setup using Portainer. It also has ffmpeg version 4.4.1 according to the logs. Added the OMV user for this container to the render privilege group as well. This is the docker-compose stack:

---
version: "2.1"
services:
 jellyfin:
 image: lscr.io/linuxserver/jellyfin
 container_name: jellyfin
 environment:
 - PUID=1000
 - PGID=100
 - TZ=Europe/Amsterdam
 - UMASK_SET=022 #optional
 network_mode: swag
 volumes:
 - /srv/dev-disk-by-uuid-aada99cb-82e3-431b-967c-1a96d6888a5a/Dionysus/Config/Jellyfin/:/config
 - /srv/dev-disk-by-uuid-057d6636-28aa-41a5-839b-99a2fae70679/Hephaestus/Media/Shows/:/data/tvshows
 - /srv/dev-disk-by-uuid-5bc250ed-b109-4bed-8f14-70d7142bbe87/Ares/Media/Movies/:/data/movies
 - /srv/dev-disk-by-uuid-5bc250ed-b109-4bed-8f14-70d7142bbe87/Ares/Media/Music/:/data/music
 devices:
 - /dev/dri:/dev/dri
 ports:
 - 8096:8096
 - 8920:8920 #optional
 - 7359:7359/udp #optional
 - 1900:1900/udp #optional
 restart: unless-stopped

I've tried to follow the Hardware acceleration guide in the Jellyfin docs, link. It seems like VA-API first has to be setup and after that Intel QuickSync can be added, it also seems like SQV is now in the standard Jellyfin image so there would be no need to install Intel drivers separately (which a guide on this forum said to do, but their GitHub hadn't been updated for a few years). Checked in /dev/dri and both card0 and renderD128 are there. 

After step 2 of the VA-API hardware acceleration part in the guide it already goes wrong, step 1 works and I get the same results as in the documentation and step 2 I checked in a log. I however don't know what to do at step 3 and step 4 gives errors. When trying to transcode something now it says some stuff in the Jellyfin logs which all end like this:


Stream mapping:
 Stream #0:0 -> #0:0 (hevc (native) -> h264 (h264_vaapi))
 Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[h264_vaapi @ 0x560739b4aa80] Driver does not support VBR RC mode (supported modes: CQP).
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
[aac @ 0x56073762d2c0] Qavg: 65536.000
[aac @ 0x56073762d2c0] 2 frames left in the queue on closing
Conversion failed!

If anyone could help or perhaps send me to a helpful tutorial (as I couldn't find one, or at least now ones that seemed out of date) that would be great.