I know not an ideal solution but after trying lots of foss applications, we decided to make our own solution. Other than that Nextcloud Deck is more than enough for most use cases

nextcloud deck, integrates well with other tools, can attach files, notes easily and has an awesome mobile app.

Lonewolf - https://flathub.org/apps/site.someones.Lonewolf

Progress - https://flathub.org/apps/io.github.smolblackcat.Progress

are some alternatives too.

I only have experience with nextcloud deck. It generally works. The permissions for other users are not very intuitive. I had problems with embedding pictures.

The android app has room for a lot of improvement. Especially regarding support for markdown.

I love Todoist and use it every day, but that may not be the use case you had in mind.

We are currently using Vikunja, I got rid of planka because it was giving way too much trouble considering the amount of features it doesn’t have.

Microsoft Planner. It integrates well with thr rest of the M365 suite, and work pays for it, so whatever.

I’m still stuck on Notion. I keep looking for OSS alternatives but nothing I’ve tried has all the features I want.

I’ve had success with Focalboard and noticed nobody is using it here! Should I look at alternatives?