OK, your TV seems to be a "HD Ready" one with a 1366x768 panel inside. RPi4 doesn't support this mode, the kernel driver filters that out, but your edid seems to contain a detailed node entry which shows up as 58Hz in kodi log and isn't filtered out.
Does it work if you append video=HDMI-A-1:1920x1080M@60 to cmdline.txt?
PS: please use the "pastekodi" script to generate logs.
so long,
Hias
Please start with a clean installation of LE10 and just add video=HDMI-A-1:1920x1080M@60D to the end of cmdline.txt (in the same line, separated by a blank from "quiet".
This should get LE into a state where you have screen output and can grab logs and your edid.
Note: if you had to add hdmi_force_hotplug=1 and manually configure hdmi modes it could also be that you have a defective cable - this isn't too uncommon and can lead to hotplug detection and/or edid reading not working.
so long,
Hias
Don't add hdmi_enable_4kp60=1 to config.txt yet - 4kp60 isn't implemented in the video driver yet and if you add that to config.txt you get the issues you described.
so long,
Hias
linuxuser sorry, my crystal ball is currently on repair. Not much we can do without a debug log or a sample to reproduce.
so long,
Hias
Maschingun thanks a lot for your edid!
Audio Data Block:
Linear PCM:
Max channels: 2
Supported sample rates (kHz): 192 176.4 96 88.2 48 44.1 32
Supported sample sizes (bits): 24 20 16
Linear PCM:
Max channels: 8
Supported sample rates (kHz): 192 176.4 96 88.2 48 44.1 32
Supported sample sizes (bits): 24 20 16
MAT (MLP):
Max channels: 8
Supported sample rates (kHz): 192 96 48
Supports Dolby TrueHD, object audio PCM and channel-based PCM
Hash calculation not required for object audio PCM or channel-based PCM
Enhanced AC-3 (DD+):
Max channels: 8
Supported sample rates (kHz): 48 44.1 32
Supports Joint Object Coding
Supports Joint Object Coding with ACMOD28
AC-3:
Max channels: 6
Supported sample rates (kHz): 48 44.1 32
Maximum bit rate: 640 kb/s
DTS-HD:
Max channels: 8
Supported sample rates (kHz): 192 176.4 96 88.2 48 44.1
Audio Format Code dependent value: 0x03
DTS-HD:
Max channels: 8
Supported sample rates (kHz): 192 176.4 96 88.2 48 44.1
Audio Format Code dependent value: 0x01
DTS:
Max channels: 6
Supported sample rates (kHz): 96 88.2 48 44.1 32
Maximum bit rate: 1536 kb/s
MPEG-H 3D Audio:
MPEG-H 3D Audio Level: Level 3
Supported sample rates (kHz): 48
Supports MPEG-H 3D Audio Low Complexity Profile
Speaker Allocation Data Block:
FL/FR - Front Left/Right
LFE1 - Low Frequency Effects 1
FC - Front Center
TpFL/TpFR - Top Front Left/Right
SiL/SiR - Side Left/Right
TpBL/TpBR - Top Back Left/RightIt looks like the TV successfully added speaker allocation map and audio formats from your soundbar. On my LG C8 I only get 2-channel PCM and no speaker allocation block - and I assume that without the soundbar your TV would provide (almost) identical information.
so long,
Hias
linuxuser could you please test this build: LibreELEC-RPi4.arm-10.0-devel-20210319162105-f44683e.tar - that should make TrueHD/Atmos available on your TV.
so long,
Hias
Thanks a lot for reporting back, and I'm glad it's working fine!
so long,
Hias
Don't get too excited, v4l2 is for grabbing from USB/PCI capture devices - for GBM hyperion will probably need to use a completely different approach (eg kodi addon that gets access to the decoded video data).
so long,
Hias
No, there's nothing you (or anyone else) can do ATM - stick to 4kp24/30 files for now.
so long,
Hias
If you tested with 4kp60 files then this is expected - the performance of the HEVC is not what it should be, the RPi video codec guru is currently working on improving that.
Playback over network can also be problematic with high-bitrate files, especially if you are using Kodi's built-in smb client and ts files. Enabling buffermode 1 in advancedsetttings, using an OS-level smb/cifs or NFS mount might help in that case.
so long,
Hias
Not sure what you mean with "will have any buffers".
so long,
Hias
As posted in the HDR thread RPi4 testbuild with HDR support BT2020 and 10/12-bit output handling are currently missing in the video driver and kodi. The RPi4 will decode 10bit 4k HDR videos up to 30fps fine, but output is not fully "proper" yet.
so long,
Hias
We don't have a release date for stable LE10 - it'll be released when it's ready. RPi4 isn't fully feature complete yet (eg no 4kp60 or deinterlacing) and the missing bits will be added over time - so we'll probably call it "beta" for a while.
so long,
Hias
Which LibreELEC version did you use? If it was 9.2.6 then please give LE10 beta1 a try.
Note that the old hdmi_xxx settings in config.txt won't have any effect in LE10 - you can use eg "video=1280x720M@60" added to the end of cmdline.txt to select a different default mode though.
so long,
Hias
Switching back to fkms will bring back screen tearing, you loose HBR audio passthrough and HDR and you won't get any support from us. Other than that you are of course free to do that - just don't complain if things don't work 
so long,
Hias
no. hyperion(ng) doesn't have a grabber supporting GBM - see also here Raspberry Pi 4 with Libreelec v19 / Kodi Matrix, no grabber is working · Issue #983 · hyperion-project/hyperion.ng · GitHub
so long,
Hias
Thanks for reporting, the issue affects all service addons. A fix will be in the next LE release Revert "kodi: service addon wrapper call fix" by HiassofT · Pull Request #5251 · LibreELEC/LibreELEC.tv · GitHub
As a workaround disable and then enable the addon again, then it'll work as expected, too.
so long,
Hias