Arrr! is a Linux daemon ( and pirate) that pulls from all those sources via plugins and puts everything into a single stream. The thing that pushed me to actually build it was the digest: I don't want a desktop popup for every RSS item, but I do want a summary of what came in overnight.
It runs as a systemd user service, loads plugins from .dll files at runtime (RSS, Telegram, WhatsApp, IMAP, GitHub, CalDAV, MQTT, Todoist), and delivers to D-Bus, ntfy, SMTP, Gotify, Pushover or any sink plugin. There's a web UI for history and config, and a small tray app for Linux desktop notifications.
Self-hosted, no cloud, single binary