My 2 cents:

Simple, no domain required stuff:

• Pi-hole for self-hosted DNS: https://pi-hole.net/
• Navidrome for self-hosted music server: https://www.navidrome.org/ (best to pair this with an external portable HDD/SSD for music storage)
• Set up syncthing on it and use it for automatic file back-up: https://syncthing.net/ (that external HDD/SSD will come in handy again).

More advanced, should pair with a domain:

• Nextcloud for your own personal cloud/calendar/etc: https://nextcloud.com/ - it won’t be blazing fast but it will work well, I had it running on a pi for a while.
• Simple web hosting - the pi is great for hosting low traffic stuff like blogs etc.

I am currently running

• Nextcloud: slow, but great for Calendar or Notes
• Gonic
• Airsonic Refix
• transfer.sh
• FileBrowser
• Conduit
• Cinny
• Mosquitto
• Prometheus
• Grafana

The last three are quite niche. I use Prometheus + Grafana for Monitoring the Pi itself and for displaying MQTT Stats. Since upgrading to SSDs performance is actually quite good, especially when taking power usage into account.

Jellyfin, I’ve run mine for a couple years now(ever since the pi4 came out) and it’s been great. The only thing to consider is turning off video transcoding, its not able to to transcode anything HD or over. Other than that, its great. I use it for videos and music.

Best is so subjective.

I am running pivpn, pihole, all the arrs, jellyfin, gitea and rundeck.

I had jellyfin, arrs, wireguard and a lot more, but adding nextcloud was too much for 4GB. It would start with 2.7 GB used, but building until it OOMs. Also rpi cant transcode, but its perfect for direct play. I upgraded my server to PC version once I had to upgrade storage. Running multiple disks from rpi requires extra cables, devices and then its not cheap small factor anymore :)

Now I have raspberry for 2nd pihole, 2nd wireguard, duckdns, upsnap (WOL) and filebrowser