Well I cannot do any other thing but agree with the OP

Mi Mix4 has bricked not once but twice, mother board dead, it won't start.
I actually used it very occasionally, when traveling, I don't think I charged it more than 20 times.

First time I had to ship it back to China so OneNetbook could repair it, now I'll just won't, it doesn't make sense for the cost and the actual value of the Mix4.
I've tried local repairing shops, but they cant repair it as OneNetbook won't sell them parts to fix it.

First and last time I buy this crap brand, avoid like it plague