Jelly-ffmpeg6 is not available: how to install ?

[Jujukeke]

Hi TheDreadPirate 

Here is an extract of my transcode log file : "Stream #0:0: Video: h264 (High), vaapi(tv, bt709, progressive), 720x572"

So:
- I tried to boot to an USB Debian 12 Live: the "renderD128" was available in /etc/dri/ ==> it should work
- I tried to boot to an USB Ubuntu Desktop 24.04 LTS; select "Try Ubuntu" (without install):  the "renderD128" was available in /etc/dri/ ==> it should work
- I tried to boot to an USB Ubuntu Server 24.04 LTS; but no "Try Ubuntu" available, so I cancelled the test. BUT unfortunalety, I discover that I crash my dual boot. My Debian 9 was no more bootable, only the Ubuntu 24.04 LTS server with i915 trouble!
- Quite disapointed, I tried to understand if it is possible to access my missing boot partition with "grub" setting (maybe not a good idea, I don't know), and see the setting 'GRUB_CMDLINE_LINUX_DEFAULT="acpi=off i915.modeset=1"'
- "i915.modetest" was one of my test to activate "i915" without success
- I set "acpi=off" at the early beginning of the installation of my new OS because on the consol of my server, several "acpi error" messages were displayed. Thanks to this parameter, no more error message ! So I tried to remove this parameter, and let   'GRUB_CMDLINE_LINUX_DEFAULT="" ' empty
- I reboot and now: 

Code:

/dev/dri$ ls
by-path  card1  renderD128

The good news, IT WORKS NOW but:
- I loose my Debian boot, any idea to restore it ? In fact, maybe I lost the dual boot after Ubuntu kernel update, but how to restore the grub menu after the BIOS?
    ==> I solved it by adding "GRUB_DISABLE_OS_PROBER=false" in /etc/default/grub
- I have a lot of "ACPI Error" messages on the display directly connected to my server (normally no screen plug on it, but, it is not cool! Any idea? (I tried ' GRUB_CMDLINE_LINUX_DEFAULT="quiet loglevel=3 splash" ' but the messages are already displayed)
    ==> No solution  


Thank you so much TheDreadPirate for all your help !!!!!!!