I already understood the nuances of ぶり that were presented here: ぶり
But what does it mean when it is attached to question words like いつぶり or 何年ぶり？
I got recently this message 学校に行くのいつぶり？
How does that differ from a simple いつ？
Well, they are quite different and the difference is not nuanced but pretty clearly shown.
When are you going to school? (When is it that you will go to school?)
When was the last time you went to school? (How much time has passed since the last time you went to school?)
Actually @Eiríkr Útlendi gave a very good explanation in the answer you cited that's hard to improve on:
When appended to a time-related noun or phrase, -buri again carries stronger connotations of "whole, entire", in terms of "the whole XX amount of time has passed". 三週間ぶり would mean "it's been three whole weeks [since ...]".