Did you also try to run myscript.sh containing python myscript.py inside to test if there's a same issue?
The another solution perhaps could be to run the python script permanently, sniffing for the commands which you could put somewhere by another script invoked by button...
OK, as mentioned earlier, I have never tested that on LE 9.2.6 so you may need to move to LE 9.80 Nightly builds where it works for sure (at least with my config options above) if the Analogue output is not enough for you.
Again, make sure to have the HDMI1 active ( a HDMI audio device connected and turned ON) when Kodi starts.
So connect a display turned ON to HDMI0 port , connect a HDMI audio device turned ON to HDMI1 port and restart RPi running LE 9.80 Nightly.
Then you can switch the Audio ouput to HDMI1 (the Audio options are a bit different from LE 9.2.6).
I am running FHD and don't know about the issue...
Perhaps a more detailed description / link to screenshot or video should be shared. I can't imagine what do you mean as on my RPi 4B (even with 1 GB RAM) with latest official LE 9.2.6 I have never seen anything like "tears in the menus".
Maybe you have a very cheap / bad / incompatible SD card?
Do you have a proper Regional settings options (Region default format / Timezone country / Timezone) in Kodi - Settings - Interface - Regional ?
For running scripts / commands by IR remote I would recommend go this way, it's reliable and easy to (re)configure, especially if you can map buttons unused by Kodi (use search to find some more examples here):
echo /usr/bin/irexec -d /storage/.config/lircrc >> /storage/.config/autostart.sh
And some example of lircrc config file:
/storage/.config/lircrc :
begin
prog = irexec
button = KEY_A
config = kodi-send --button=a
end
begin
prog = irexec
button = KEY_TITLE
config = /storage/signalshow/sigshow.sh
end
begin
prog = irexec
button = KEY_POWER2
config = /storage/relay/togglerelay.sh
end
begin
prog = irexec
button = KEY_PRINT
config = kodi-send --action="TakeScreenshot"
end
begin
prog = irexec
button = KEY_MODE
config = kodi-send --action="ActivateWindow(Settings)"
end
begin
prog = irexec
button = KEY_FAVORITES
config = kodi-send --action="ContextMenu"
end
No problem. 
I can't now check what are the options on LE 9.2.6 as I am yet using LE 9.80 Nightly where it works as I mentioned above.
But you should be able to change the Audio output device on LE 9.2.6 for sure somehow. At least on fresh LE 9.2.6 installation and at least you should be able to select between HDMI audio and Analog output (or both at the same time).
Not sure about HDMI1 audio output on LE 9.2.6 - I have never tested there.
Regarding to relevant config - among others, I have this option in RPI's bootloader configuration (vcgencmd bootloader_config) :
DISABLE_HDMI=0
And these options in /flash/config.txt (not sure if the HDMI options works or not, you may play with Video options in config.txt - Raspberry Pi Documentation :
# Enable audio jack output
dtparam=audio=on
#forcing the Pi to ignore port 0
hdmi_ignore_hotplug:0=1
#forcing the Pi to use port 1
hdmi_force_hotplug:1=1
hdmi_ignore_edid:1=0xa5000080
hdmi_group:1=2
hdmi_mode:1=82
hdmi_cvt:1=1920 1080 60 6 0 0 0
hdmi_drive:1=1
hdmi_ignore_cec_init:1=1
There's no mention about device model nor LE version that you are using and it may differ.
In general you need to change the Audio options in Kodi - Settings - System - Audio - Audio output device.
You also need to have the HDMI1 active (the device connected turned ON) when Kodi starts.
It works fine when configured properly (audio on HDMI1 while video on HDMI0) at least on RPi 4B running LE 9.80 Nightly builds ( Index of / ).
There are 2 things mixed, the bootloader itself and the bootloader configuration.
I believe you already have the bootloader you need (although maybe not the latest available) installed.
The firmware version check / update can be easily done from Kodi - Settings - Libreelec - Updates - Firmware Updates
So you can easily upgrade the bootloader and VIA USB firmware to versions contained in your LE package which are quite fresh.
A manual upgrade way is described here: RE: Is it possible already to set up a rpi4 with kernel 5.4?
There's also outlined how to show the bootloader configuration. If you wish to edit it, you must be at least able to connect to your RPi through SSH client (Putty recommended) and use nano editor. Both Putty and nano are easy to use. Default username is root, password libreelec.
After connecting to your LE, copy and paste these commands:
cd /tmp
vcgencmd bootloader_config > bootconf.txt
nano bootconf.txt # edit the current bootloader configuration as you wish, then press CTRL+X, Y, ENTER to save file
rpi-eeprom-config /tmp/pieeprom.bin --config /tmp/bootconf.txt --out /tmp/pieeprom
rpi-eeprom-update -d -f /tmp/pieeprom
reboot
You are not limited to SD card only, try USB 3.0 flash stick or SSD connected through USB 3.0 adapter.
Of course you can change the bootloader configuration, it's the same process in LE as in RPi OS (just without sudo as in LE you are root by default).
Raspberry Pi 4 bootloader configuration - Raspberry Pi Documentation
Also read here:
Yeah but it's strange that dead links are always much more easy found...
Regarding to config.txt read here: Where is config.txt
Unfortunately the links to wiki are dead...
Do you get any response when you run the irw command and push MENU button on your RC?
Where do you run the command from?
Edit: Use SSH console to run the command and see the output.
In case you refuse all offered solutions, you should perhaps select another platform instead (RPi OS + Kodi)?
No problem. You may also look here for many other Video parameters for use in /flash/config.txt :
Video options in config.txt - Raspberry Pi Documentation
Perhaps you may try to force some HDMI mode which could possibly help to do what you need...
Yes it's always good to share...
No, I don't see any obvious issue.
The VL805 firmware release 000138a1 is the latest available.
Your bootloader dated 2020-09-03 is currently default/critical so it's also not bad but I would go to latest available and yet stable version 2020-12-11
You may see details here:
rpi-eeprom/release-notes.md at master · raspberrypi/rpi-eeprom · GitHub
The bootloader config looks also default, I am using a more complex/customized, like this:
[all]
BOOT_UART=0
WAKE_ON_GPIO=0
POWER_OFF_ON_HALT=1
DHCP_TIMEOUT=45000
DHCP_REQ_TIMEOUT=4000
TFTP_FILE_TIMEOUT=30000
ENABLE_SELF_UPDATE=1
DISABLE_HDMI=0
BOOT_ORDER=0xf41
USB_MSD_PWR_OFF_TIME=3000
USB_MD_LUN_TIMEOUT=5000
A detailed config params description:
Raspberry Pi 4 bootloader configuration - Raspberry Pi Documentation
Even with your current bootloader release, you should be able to directly boot LE 9.2.6 or LE 9.80 nightly from USB flash / disk, AFAIK all you need to do is to image it like it was your SD card (and maybe to add the preferred BOOT_ORDER parameter to bootloader config), connect to USB port, remove the microSD card and boot.
Then it was necessary to put this line to /flash/config.txt in LE:
dtparam=sd_poll_once=on
otherwise there was a repeating error message filling log due to missing SD card (not sure if it's still necessary).
Well, I don't see a big difference... Maybe a some timing issue?
As outlined earlier, I would try to:
double check the current mappings which should be exactly the same at the moment on both installations:
ir-keytable -r -s rc0
I would then run the irw command on LE 9.80 and press / release any RC button quickly to check online what happens - if you receive always the same number of commands (instead of just one) or if it is so sensitive to length of the push (and you receive for instance sometimes 3, sometimes 5 or even more commands in quick sequence).
You may also try to play with -D and -P parameters of ir-keytable to increase default autorepeat values.
-P, --period=PERIOD Sets the period to repeat a keystroke
-D, --delay=DELAY Sets the delay before repeating a keystroke
If nothing works, I would try to make a backup and install the latest fresh LE 9.80 Nightly from scratch.
