Just updated my ASROCK J4105-ITX to 6.3.2 with you drivers. All looks finally fine now (in 6.2.2 it was not possible to get hw transcoding working):
root@synology01:~# ls -lah /dev/dri/
total 0
drwxr-xr-x 2 root root 80 Apr 22 13:54 .
drwxr-xr-x 15 root root 19K Apr 22 13:55 ..
crw------- 1 root root 226, 0 Apr 22 13:54 card0
crw------- 1 root root 226, 128 Apr 22 13:54 renderD128
root@synology01:~# cat /var/log/dmesg | grep drm
[Wed Apr 15 07:21:00 2020] [drm] Initialized drm 1.1.0 20060810
[Wed Apr 15 23:32:18 2020] [drm] Initialized drm 1.1.0 20060810
[Fri Apr 17 22:11:16 2020] [drm] Initialized drm 1.1.0 20060810
[Wed Apr 22 13:54:27 2020] [drm] GuC: No firmware known for this platform!
[Wed Apr 22 13:54:27 2020] [drm] HuC: No firmware known for this platform!
[Wed Apr 22 13:54:27 2020] [drm] VT-d active for gfx access
[Wed Apr 22 13:54:27 2020] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[Wed Apr 22 13:54:27 2020] [drm] Driver supports precise vblank timestamp query.
[Wed Apr 22 13:54:27 2020] [drm] Finished loading DMC firmware i915/glk_dmc_ver1_04.bin (v1.4)
[Wed Apr 22 13:54:28 2020] [drm] failed to retrieve link info, disabling eDP
[Wed Apr 22 13:54:30 2020] [drm] GPU HANG: ecode 9:0:0xa0b1a191, reason: Hang on bcs0, vcs0, vecs0, action: reset
[Wed Apr 22 13:54:31 2020] [drm:gen8_reset_engines [i915]] *ERROR* bcs0: reset request timeout
[Wed Apr 22 13:54:33 2020] [drm:gen8_reset_engines [i915]] *ERROR* vcs0: reset request timeout
[Wed Apr 22 13:54:34 2020] [drm:gen8_reset_engines [i915]] *ERROR* vecs0: reset request timeout
[Wed Apr 22 13:54:37 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:39 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:42 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:42 2020] [drm] Initialized i915 1.6.0 20171222 for 0000:00:02.0 on minor 0
[Wed Apr 22 13:54:42 2020] [drm] Cannot find any crtc or sizes
[Wed Apr 22 13:54:42 2020] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
root@synology01:~# cat /var/log/dmesg | grep i915
[Wed Apr 22 13:54:27 2020] [drm] Finished loading DMC firmware i915/glk_dmc_ver1_04.bin (v1.4)
[Wed Apr 22 13:54:30 2020] i915 0000:00:02.0: Resetting bcs0 after gpu hang
[Wed Apr 22 13:54:31 2020] [drm:gen8_reset_engines [i915]] *ERROR* bcs0: reset request timeout
[Wed Apr 22 13:54:31 2020] i915 0000:00:02.0: Resetting vcs0 after gpu hang
[Wed Apr 22 13:54:33 2020] [drm:gen8_reset_engines [i915]] *ERROR* vcs0: reset request timeout
[Wed Apr 22 13:54:33 2020] i915 0000:00:02.0: Resetting vecs0 after gpu hang
[Wed Apr 22 13:54:34 2020] [drm:gen8_reset_engines [i915]] *ERROR* vecs0: reset request timeout
[Wed Apr 22 13:54:34 2020] i915 0000:00:02.0: Resetting chip after gpu hang
[Wed Apr 22 13:54:37 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:39 2020] i915 0000:00:02.0: i915_reset_device timed out, cancelling all in-flight rendering.
[Wed Apr 22 13:54:39 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:42 2020] [drm:gen8_reset_engines [i915]] *ERROR* rcs0: reset request timeout
[Wed Apr 22 13:54:42 2020] i915 0000:00:02.0: Failed to reset chip
[Wed Apr 22 13:54:42 2020] [drm] Initialized i915 1.6.0 20171222 for 0000:00:02.0 on minor 0
[Wed Apr 22 13:54:42 2020] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
Thank you very much!