For quite a long time I was interested in Freemasonry, but never had enough time and motivation to go deeper and explore this question in details.

First of all, it is not really clear whether this is a religious institution or not. They position themselves as a non-religious, non-political, fraternal and charitable organisation. You can belong to whatever religion you like and join them. Actually, the first requirement to become one of them you should believe in God, but you can not discuss religion on the masonic meetings.

There is a lot of controversy about this topic and the best article I found is: Is Freemasonry a Religious Institution?

Of course, you should read it with some level of scepticism as other religious institutions have been always against masonry, especially Christianity.