I have finally found some time to try the SD install for 7.0.2.005 and I have not been able to get LE to boot.
My MXQ Pro+ is running OE 6.95.3 from SD with balbes150's S905_autoscript. I am also running a Tronsmart Meta rom compiled by sd-robots. The original firmware was terrible. OE runs pretty well with no boot issues.
This box has no reset switch in the AV hole, so I can't use that method. The firmware does not offer a reboot to recovery option, so I tried Quick Boot, which boots me into TWRP. I replaced the original MBOX recovery with TWRP so that I could flash sd-robots/Tronsmart Meta rom.
I tried ADB, adb reboot recovery, the box booted into TWRP.
I tried ADB, adb reboot recovery, with a USB with s905_autoscript and SD card with 7.0.2.005 extracted onto it - booted into TWRP.
I tried the USB/SD combo with the S905_autoscript on the USB stick - USB OTG port, booted at the same time as the SD card - the first time it booted into Android and then went through an 18 app optimization then Andoid started. I rebooted and the box went straight to Android.
The S905_autoscript is on both the USB and SD cards when booted - not sure if this was correct.
I would appreciate any help/advice on how to get LE to boot. I can't think of anything else to try.
JonSnow tried it by using the update and backup app in android, then selecting update and when it searched for zip files, selecting a zip from the kodi add-ins. When it rebooted, it executed the script on the SD card to be able to boot from SD and load LibreElec. I did the same thing on my MXQ Pro 4k as I was also stuck in your situation and it worked.