Can I get this letter from Board Director of well-established Telecommunications company whos experience in customer delivery, systems integration?
Can I get this letter from CTO of trade and transport well-established company who fulfill all import, export, and transit-related regulatory requirements?
Can I get this letter from CTO of well-established bank?
I don’t think there were hard rule about that. Let’s say you won a major international hackathon - and the head of the jury wants to give you the recommendation. That would mean you knew each other for one day - which I think still fine.
Nevertheless, the recommendation should be backed up by some facts/data why the person signing the letter thought you may be considered a leading talent. The important thing is that data should be genuine and verifiable, opinions may be less relevant unless the recommendation is from the well-known industry expert that literally everybody knows and respects.
I would suggest that you should get recommendations from people who know your professional work well and can write about it at some level of depth (both the what and the how). If it is a trade off, get someone who knows you well to write the letter, compared to one who has a fancier resume or title, but knows you too little, and the recommendation letter ends up appearing shallow.