What eink device? I recently switched from a locked-down kindle to a very open android Boox.
I have Syncthing installed on it and when I want to read something later I either bookmark it with a particular tag (to a self-hosted bookmarks app that I can access from the eink) or if it's weirder - like a nostr post or a PDF - I drop it in a "read later" Syncthing folder.
This is admittedly not ideal since I'd have to somehow export the nostr post as a PDF, markdown, or other archive style, but it does get the job done.