My Pi4 (8GB ram) runs:

1. Mox mail server at home (PTR record set up with ISP) - https://github.com/mjl-/mox.

2. Web server (no external hosting hurray); TLS set up via LetsEncrypt.

3. Navidrome for streaming my music collection to my phone/computers. I ripped my thousands of CDs to MP3. I use subtracks on my phone for listening to it, and sonixd on my computers (Mac/PC). https://github.com/navidrome/navidrome

4. mpd for driving some speakers via a USB audio interface so I can use some speakers plugged into the Pi for listening to music in the same room as the Pi (practicing guitar). I control this via the Supersonic app on my phone.

5. Wireguard VPN so I can connect home.

6. PiHole for my network at home. Combined with Wireguard, it means my phone is permanently connected to my home network and gets ad-blocking and stops apps dialing home. I use DroidHole on my phone to see what's going on.

7. xrdp server running, so a usable desktop is always available.

8. miniDLNA running connected to a NAS box so that I can watch all my DVDs easily on my TV downstairs (I spent weeks ripping them).

9. Tuya IoT API for turning some smart plugs in the house on/off via cronjob; I do this instead of using the timer in their app because it means my phone can be off the network/abroad and these plugs/lights still turn on/off.

10. linx-server (https://github.com/andreimarcu/linx-server) for sharing files so that I don't have to use Google Drive and share with people that way.

11. Peer Calls (https://github.com/peer-calls/peer-calls) so I can video conference in decent quality without having to use Google Meet / Teams etc. I also host a STUN and TURN server on the Pi so that Peer Calls works behind NAT.

12. Runs CUPS so that my very cheap Samsung wireless laser printer actually shows up as an AirPrint printer for my wife's iPad/iPhone and shows up in Android printing. (The printer does not natively have AirPrint capability but CUPS means I can provide it to users on the network).

It fetches time over NTP on a cron job. It also blocks various ASNs and IPs by country on a cron job to stop annoying remote pests and cloud providers. It also runs Monitorix so I can see system load, and goaccess on a cron job so that I can see who's hitting my website without having to resort to analytics nonsense.

It boots from USB3 (it has a NVMe in an IcyBox caddy).

Incredibly useful device.