Hiya! Headspace was useful for me for sure. And i can very much relate to the mind wandering aspect, it still happens to me a lot. I stopped HS as I had to make various budget cutbacks (not that is matters here of course for the free parts) and am actually using an App called Peace now, as I answered some of their questions on a reddit thread and got the premium for doing so. Overall I would say Headspace offers a better package but if you are looking around for other free apps then Peace is worth looking at.
Whatever you find, I hope it continues to help. I must say that when I haven’t sat for a few days, I notice the difference a lot now. So I am really trying to do this at least once every other day (life stuff very much in the way right now).