No Docker unfortunately, it would require either to recompile the mobile Kernel or use QEMU and I believe it would have a big impact on the performances. Basically this time the approach was: what can I do with an old mobile without rooting or anything. Hardware:

• Samsung S20
• USB3 to Ethernet & charger port
• 128GB SD card

Sofrware:

• Termux (android app)
• SSH (OpenSSH in Termux)
• Rclone (in Termux)
• Sonarr, Radarr, Lidarr, Prowlarr (in proot-distro)
• Transmission (in proot-distro)
• Kavitha (in proot-distro)
• Podgrab (in proot-distro)
• Ombi (in proot-distro)
• ntfy (in proot-distro)
• Filebrowser (in proot-distro)
• Vaultwarden (in proot-distro)
• Homer with lighttpd (in proot-distro)

Since I wasn't able to install .NET Runtime in Termux directly, I used the proot-distro (Ubuntu) and inside I've installed all the services. Services are started manually every time I restart the proot-distro (unfortunately I'm getting an error when installing Termux:Boot), it's a simple script so I'm not dying over it. To keep the proot-distro alive I launch is with the screen command so I'm ensuring persistence even when the terminal is closed.

It's not a clean solution like docker etc. but I'm consuming 5 or 10Wh of energy every day which is close to nothing and probably sustainable with a solar panel.

Every once in a while (basically when the SD is almost full) I transfer the files with rclone to an external drive where I consolidate the files.

Oh extra tip, with rclone you can create a DLNA server so you can serve the files you have download immediately (tested with VNC and Kodi)

The phone/server has still room (CPU & RAM) to go and possibly I could install HomeAssistant without any issue. Also I could add Joplin and Floccus using webdav for storage as I had in my previous server but I don't miss them.

Any other questions, doubts, scripts, feel free to ask!