Old and slow SD cards are great for debugging issues with problemattic boot because they don't support the faster access modes which can trip an Amlogic silicon bug causing mmc device instability. The kernel has a workaround for the bug but it's not perfect (perfect doesn't exist) and issues do arise sometimes. Old slow cards also negate the need for custom device-trees in most cases.
If you edit uEnv.ini and change "quiet" to "quiet ssh" (adding ssh to boot params) the SSH service is forced on and you can probably access the box to run "pastekodi" and share the URL so we can see the system log and kodi log to look for service start failures and other issues.
NB: please use the "box" image here: https://chewitt.libreelec.tv/testing/ as it has some extra things inside to help testing (maybe).