You can safely delete the core files:
find /storage/.cache/cores/ -type f -deleteBut most likely the failtng process continues crashing and generating core files. Keep an eye on the folder and post the output of ls -l /storage/.cache/cores when new files arrive.
LibreELECs du command is using a block size of 512 bytes by default.
scaling_cur_freq should be available for intel_pstate driver too, try:
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freqcat /sys/bus/pci/devices/0000:00:02.0/drm/card0/gt_cur_freq_mhz
That is the video clock of the GPU.
Use
cat /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_cur_freqto see the current CPU core frequencies.
Does it work at boot if you add the trigger to autostart.sh?
echo udevadm trigger >>/storage/.config/autostart.shusb_modeswitch is part of the LibreELEC System Tools addon.
<setting id="audiooutput.eac3passthrough" default="true">false</setting>I have no knowledge about possible hardware/software limitations of the RPI but EAC3/DD+ passthrough is disabled in your configuration.
"new Thinclient" is not much technical information...
You can save the install log on usb stick after installation.
[ 72.816379] mmc0: tuning execution failed: -22
[ 74.055580] mmcblk0: error -110 requesting status
[ 74.206826] mmc0: cannot verify signal voltage switch
[ 74.861183] mmc0: tuning execution failed: -22
[ 76.098784] mmcblk0: error -110 requesting status
[ 76.250210] mmc0: cannot verify signal voltage switch
[ 77.312889] mmc0: tuning execution failed: -22
[ 78.552061] mmcblk0: error -110 requesting status
[ 78.703483] mmc0: cannot verify signal voltage switch
[ 82.883572] mmc0: tuning execution failed: -22
[ 84.135352] mmcblk0: error -110 requesting status
[ 84.286642] mmc0: cannot verify signal voltage switch
[ 84.947272] mmc0: tuning execution failed: -22
[ 86.188871] mmcblk0: error -110 requesting status
[ 86.340185] mmc0: cannot verify signal voltage switch
[ 86.999573] mmc0: tuning execution failed: -22
[ 88.238705] mmcblk0: error -110 requesting status
[ 88.389840] mmc0: cannot verify signal voltage switch
[ 89.116211] mmc0: tuning execution failed: -22
[ 90.355461] mmcblk0: error -110 requesting status
[ 90.506648] mmc0: cannot verify signal voltage switch
[ 91.286243] mmc0: tuning execution failed: -22
[ 92.538780] mmcblk0: error -110 requesting status
[ 92.690448] mmc0: cannot verify signal voltage switch
[ 93.446115] mmc0: tuning execution failed: -22
[ 94.685429] mmcblk0: error -110 requesting status
[ 94.836741] mmc0: cannot verify signal voltage switch
[ 94.950034] print_req_error: I/O error, dev mmcblk0, sector 5234520
[ 95.489538] mmc0: tuning execution failed: -22
[ 96.728672] mmcblk0: error -110 requesting status
[ 96.880090] mmc0: cannot verify signal voltage switch
[ 97.529654] mmc0: tuning execution failed: -22
[ 98.768698] mmcblk0: error -110 requesting status
[ 98.768705] mmcblk0: recovery failed!
[ 98.768721] print_req_error: I/O error, dev mmcblk0, sector 5234680
[ 103.482005] mmcblk0: error -110 requesting status
[ 103.633371] mmc0: cannot verify signal voltage switchTime to exchange your SD card.
3181944kB kodi.bin RSS size in 4141 seconds (from dmesg) is unlikely for the found slow growing memory leak.
In the crash log there are a lot of
2019-06-15 21:10:02.489 T:139781078423296 NOTICE: VAAPI::Close
2019-06-15 21:10:02.489 T:139780029404928 NOTICE: COutput::OnExit: Output Thread terminated
2019-06-15 21:10:02.494 T:139780029404928 NOTICE: COutput::OnStartup: Output Thread createdat the end before crashing in
Thread 1 (Thread 0x7f2151869700 (LWP 976)):
#0 0x00007f2168678661 in vaDestroyContext () from /usr/lib/libva.so.2
#1 0x00007f216781bf0c in ?? () from /usr/lib/libavcodec.so.58
#2 0x00007f216745a88a in ?? () from /usr/lib/libavcodec.so.58
#3 0x00007f216753c705 in ?? () from /usr/lib/libavcodec.so.58
#4 0x00007f216753d551 in ?? () from /usr/lib/libavcodec.so.58
[...]Looks like "something" fails an then run out of resources. 
Updated mesa and/or kernel driver may help on your hardware but there is no guaranty.
Change systemd's reboot behavior. Copy /usr/lib/systemd/system/reboot.target (or .../systemd-reboot.service) to /storage/.config/system.d and change it to your needs.
By reading Ubuntu and UEFI on Lenovo Thinkcentre M92P · GitHub the M92 seem to be designed as Windows only device 
You can try to create a fake UEFI boot entry as described in the linked solution. Boot the installer in UEFI mode and use <Alt>-F3 to get a console.
Maybe you did boot the USB installer in legacy mode and the system is using EFI afterwards.
If the USB stick is listed twice in boot menu try the other entry.
Thread 1 (Thread 0x5a797370 (LWP 827)):
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1 0x74d8b184 in __GI_abort () at abort.c:79
#2 0x74ca28b0 in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/libstdc++.so.6
#3 0x74ca05ec in ?? () from /usr/lib/libstdc++.so.6
#4 0x74ca0660 in std::terminate() () from /usr/lib/libstdc++.so.6
#5 0x74ca09c8 in __cxa_throw () from /usr/lib/libstdc++.so.6
#6 0x74ca0fd4 in operator new(unsigned int) () from /usr/lib/libstdc++.so.6
#7 0x74ce481c in std::string::_Rep::_S_create(unsigned int, unsigned int, std::allocator<char> const&) () from /usr/lib/libstdc++.so.6
#8 0x74ce5864 in std::string::_Rep::_M_clone(std::allocator<char> const&, unsigned int) () from /usr/lib/libstdc++.so.6
#9 0x74ce5920 in std::string::reserve(unsigned int) () from /usr/lib/libstdc++.so.6
#10 0x74ce5e7c in std::string::push_back(char) () from /usr/lib/libstdc++.so.6
#11 0x6a03eb5c in PVRIptvData::GzipInflate(std::string const&, std::string&) () from /storage/.kodi/addons/pvr.iptvsimple/pvr.iptvsimple.so.3.5.7
#12 0x6a0401e8 in PVRIptvData::LoadEPG(long, long) () from /storage/.kodi/addons/pvr.iptvsimple/pvr.iptvsimple.so.3.5.7
#13 0x6a03f264 in PVRIptvData::GetEPGForChannel(ADDON_HANDLE_STRUCT*, PVR_CHANNEL const&, long, long) () from /storage/.kodi/addons/pvr.iptvsimple/pvr.iptvsimple.so.3.5.7
#14 0x6a03d00c in GetEPGForChannel () from /storage/.kodi/addons/pvr.iptvsimple/pvr.iptvsimple.so.3.5.7iptvximple is terminating kodi while decompressing EPG data. Maybe OOM, check dmesg/journalctl.
Remove the EPG data to fix the crash.
I currently have the old wifi dongle and the new one connected.
... and the system is only using the old wifi dongle.
Please use the new one only. On the other side I cannot promise this will show anyrhing.
To just have 5.1 on a soundbar use TV (AC3) configuration from Audio quickstart guide - Official Kodi Wiki
You can check the configuration by downloading and playing the AC3 test file from TFM Group Software. It works if you hear the LFE test.
Unlike Windows where you can navigate around changing drivers and power / driver settings, this is a little intimidating. A6200/A6210/WNDA3100v2 wireless adapter intermittently disconnects | Answer | NETGEAR Support
There is no interactive interface. After installing the Network Tools addon from the LE repo you can use the iw* command line tools to configure wireless parameters.
But I cannot promise that you find a similar option.
Please remember to remove your copied firmware files when testing this.
