Being a flutter dev (and shameless fanboy) I will suggest people try:
appflowy - a FOSS near-clone to Notion.
spotube - FOSS music streaming using the spotify API for metadata and youtube for music playing/downloading. Completely free of ads and works surprisingly well as long as the music you like is mirrored to YouTube.
honourable mentions:
Plex, Nextcloud, Radarr, Sonarr, qbittorrent. Not your usual apps for these kinds of threads but they’re absolutely top-tier for linux home servers.