some mail clients, like thunderbird, can also handle rss feed, you then have an all-in-one solution.

For instagram, maybe look if there are pixelfed apps.

For whatsapp, I think the matrix protocol is similar, the official app is element.

Good!

I heard about wifibox before, sounds great.

For your notes, you can also use a modular approach, like :

• a real text editor to type markdown/orgmode
• a syncer to sync your devices
• a converter to produce pdf or so if needed

Sure, it's a question of taste.