Buffer documents a number of workflows and limitations in their FAQs.
E.g. for a non-professional Instagram account, the user gets a notification to manually share a post via the Instagram app.
> you can prepare your post in Buffer, receive a notification on your mobile device when it’s time to post, then tap the notification and copy your post over to the social network to finish posting.
Postiz docs show that users can create an app on Facebook and use that key and it will auto post.
I guess using POSSE for Instagram forces you to either create a personal app on Facebook which is not easy or make your Instagram account a business account.
0. https://buffer.com
1. https://github.com/gitroomhq/postiz-app