Your best bet is probably PostmarketOS, its not debian but alpine, but does support the phone and aparrently still gets some updates.

Theres a link on the page to the non T variant with flashing instructions.

https://wiki.postmarketos.org/wiki/OnePlus_5T_(oneplus-dumpling)

It should work as long as it can reach the internet

I’m not really a fan of cloudflare tunnels, but I guess thats an option too

You can’t expose ports on mobile data. You can ether host the web server at home or on a vps or use something like tailscale.

You could try tunneling usb from the host into wine with usbip, but I have a feeling that this wouldn’t work

I use traefik, but caddy should work too. I can share the docker-compose files I use later.

I didn’t understand the docs either, that’s why I’m using https://github.com/girlbossceo/conduwuit insted

ZFS doesn’t require lots of RAM, more RAM just improves the caching (ARC) it can do. You can set ZFS to use all unused RAM as ARC, so it doesn’t interfere with other services running on the same PC. I ran ZFS with lots of VMs on an old office PC with 16GB RAM and it was still able to max out a 10gig nic.

An alternative would be to boot into the bios and shut down from there