Just wondering if anybody has found permanent solutions to this problem of simple lightning strikes causing the ELCB to trip ?

Hi Boon,... if it is too sensitive, I regard it as an overkill. It will not be protecting our equipment against overcurrent conditions and voltage surges anymore, it will instead contribute two undesired effects, namely :-

1) Unreasonably tripping the mains supply and causing us inconvenience to go reset it at the DB position.
2) Compromising certain functions oi the house when the trip occurs unnecessarily, eg spoiling food in the fridge, removing CCTV Security, etc,....

Hence, I believe it is more preferred to have an ELCB that trips ONLY upon ACTUAL 'danger' conditions, and not on all possibly 'danger' conditions.

Technically, why does a good earth need to be in-place in order for nuisance trips not to take place ?

MY house has many external points in the garden, backyard, rooftop garden, etc,... which are exposed to the weather. I have isolated all these points first right when I hear distant thunder. The self-tripping has been reduced since.

Then I need to isolate which loop the culprit is and work on that loop.

Start by working on your external points/loops first.