Alpine Linux★★★★★Lightweight Linux distribution with modern capabilities and smooth package management despite its low resource requirements. Good for small cloud servers, old hardware, Raspberry Pi, etc.
DAVx5★★★★★Background app that syncs your non-Google cloud accounts with your Android system calendars and contacts.
FeatherPad★★★★★A lightweight, fast, stable, and capable text editor for Linux.
Floccus Bookmarks Sync★★★★★Very flexible, syncs across many different desktop browsers and mobile devices, and for privacy it can run on your own server or encrypted on another cloud service.
GoToSocial★★★★☆A lightweight Fediverse server, with a clean web interface for viewing public posts. Compatible with Mastodon apps and interacts with other ActivityPub platforms.
Jellyfin★★★★★Great for playing music across my local network, doesn't phone home to a cloud or try to upsell subscriptions.
K-9 Email★★★★☆Classic email app for Android: No frills, no ads, no tracking. Supports multiple accounts, phone-to-tablet layouts, and dark mode.
KeePass Password Managers★★★★★KeePassXC, its browser extension, and KeePass2Android are a nice, clean set of apps to manage your passwords on your OWN desktop and mobile devices, auto-fill websites and apps, and sync over your own server or cloud provider.
KeePass2Android★★★★★Nice, clean interface to a KeePass2 database with auto-fill support for both websites and apps and seamless syncing over your own server or the cloud of your choice.
Liferea★★★★☆A nice, lightweight feed reader for Linux that does the basics.
Manyverse★★★★☆Takes the pain out of setting up and running SSB. Unfortunately it doesn't overcome SSB's inherent challenges of discovery, data size or multiple devices. (So far?)