This is neat solution, you’ll lose the laptop WiFi internet access though.
You can set the pi to connect to the phone WiFi by editing files on the SD card (using your laptop)
https://desertbot.io/blog/headless-raspberry-pi-4-ssh-wifi-setup-64-bit-mac-windows
Pi4 with 2TB SSD running:
HDMI cable straight to the living room Smart TV (which is not connected to the internet).
Other devices access media (TV shows, movies, books, comics, audiobooks) using VLC DLNA. Except for e-readers which just use the Calibre web UI.
Main router is flashed with OpenWrt and running DNS adblocker. Ethernet running to 2nd router upstairs and to main PC. Small WiFi repeater with ethernet in the basement. It’s not a huge house, but it does have old thick walls which are terrible for WiFi propogation.
I’m interested to see how EU will measure battery life, I’m guessing some standard stress testing software perhaps?
This is how gsmarena does it: https://www.gsmarena.com/gsmarena_lab_tests-review-751p6.php