Way back when I first tried switching to using Open Source alternatives to my previous apps, I wanted a Quicken alternative and tried GnuCash. Opening the help for the first time, I found it hilarious and ever so "open source software" of them that the help document opened with a whole chapter on how double book accounting worked, because of course you'd need to know that if you wanted to use GnuCash well.
Anyway, while it wasn't the best user experience, it was a pretty good introduction to double entry accounting: https://www.gnucash.org/docs/v4/C/gnucash-guide/basics-accou...