You are giving away such a wonderful product for free and you are not asking any money for that …
I have been using Ghost Blog https://blog.nearbyshops.org/ as self-hosted version but i will be happy to donate you … !
You should actively ask people to donate you … because lot of people are benefitting from Ghost Blogging Software and they are not paying you anything !!!
You should ask and let them know that you’re open to donations !
You have No donate button on your website ? People don’t even know that you are open to donations !