That's a great find, as I'm in a somewhat similar place - (re)-learning maths at a not so young age, with kids, and doing it for the same reasons as the author. There is plenty of material out there for free (including a lot of complete courses from top universities), but not a lot of that is structured and I was often finding myself 'not knowing what I don't know'. Surprisingly, I've found chatGPT quite good for helping in that.

My current method is watching a lot of videos and taking notes - it's great in the beginning when it's mostly rediscovering what I already knew, but anything that's really new - it takes orders of magnitude more time. And that's very hard without some structure in learning.

I'm definitely giving Math Academy a try - looks great for what I need.