• Readeck is kind of a 'read it later' app.
• Karakeep is for saving data like web sites etc, that you'd like to preserve the content thereof.
• LinkWarden is for links, bookmarks tho you can use it like Readeck.
• Walabag: I've never used it but I've heard good things about it.

Others can be found here: https://openalternative.co/alternatives/pocket