This is great. And it send me down the path of trying to get my library card to work.
Turns out it uses a format called Codebar which is from 1972 and not supported by Apple wallet passes. This tool and most of the other linked ones in this thread did not work. (And also tried to charge me a recurring subscription to use once, but that’s another issue)
I found this one which generates many other barcode formats and generates them as images as a workaround. That seems to work.
I've been using Pass4Wallet (the app you linked) for a number of years and it's been fantastic. I'd recommend it.