I'm learning traditional Chinese, and have heard/seen examples of 簡筆字, like how 聽 can often be written as ⿰口耳 in Taiwan. Every time I try to look this up, I just get directed to the same Quora thread mentioning it, the Ryakuji wikipedia page, and 簡體字. Now I realize that there can be similarities between 簡筆字 and 簡體字, but there also are differences, case and point with 聽.
So I was wondering if there were any resource on their use, where they are used, how they are used, as well as a reference to common practices. Like does 門 become 门 in Taiwanese 簡筆字 like in 簡體字 or Japanese Ryakuji, or is it always written 門.