Hi,
I’m thinking of getting the Geekworm Raspberry Pi 4 UPS X703, however how does it connect to the PI to work as a UPS?
https://www.amazon.co.uk/Geekworm-Raspberry-Ultra-compact-18650-Shield/dp/B09HZXDN8S/ref=sr_1_10?keywords=raspberry+18650&qid=1675431731&sr=8-10
From the product details it looks as if there are pins on the UPS board which connect with the underside of the RPi.
May I ask why you want a UPS? If the power goes off, presumably all the devices controlled by HA will go down - giving a whole mess of errors if HA is stil running. 
It’s mainly for the alarm as the motion sensors are all battery powered and the siren has a battery backup inbuilt.
Just bought an argon one case so doesn’t look like this would fit anyway now.
Any decent options for an argon one case or should I just get a powerbank with pass through charging?
Also is there any way to setup this so that if power goes down for the internet router it then uses a SIM card dongle as a backup?