No Ads

If a notification sends me an ad, I will block the app and also review whether I even need it. Anyone willing to shovel ads at me in my notifications is not my friend.

Other stuff is simple:

• If I need to know the information right away I allow a notification. Stuff like calls, messages, server monitoring, security, etc. Notifications that only fire when actively using or just after using an app also get to stay on if they are useful.
• If it’s not urgent, I set a reminder in my to do list to review it on a recurring basis, for example “check Mastadon, weekly, Saturday”

Follow up question: how do you handle apps that have persistent notifications?

You can sync Obsidian with your own storage location. There are plugins to do a lot of what you’re asking for. Downside is that it’s not open source, though your content is all stored in plaintext so you won’t lose it due to lock-in. It also might be more than your asking for and a simpler, more tailored, solution may be out there. Paired with a self hosted Nextcloud server, you may solve a bunch of your PIM needs at once.