Add external SSD

I like to add an external SSD so I can store more sensor data and don’t wear-out my sd-card.
Only this is harder then it should be. In the device data I see HA has found the ssd as SDA1.
Only I can’t use it. Even mounting it manually doesn’t work because as root i’m not having root privileges.
So that is the suggested method for adding an external SSD in HA. I only found outdated info so far.

What is your hardware? Rpi4?
What is your installtion method. HAOS?
What SSD are you trying to install?
What …?

I assume adding an usb mass storage device to HA is very generic . Like mounting it in Linux.
So I’m curious what all those What are making a difference in the solution?
I’m using a PI4 with and i’m connecting a USB3 1TB SSD with ext4 FAT.
Thanks for the help.

Ah,ok reading again. Skip the sd card and boot it all from the SSD. You will find guides to do that (google).
I added SSD first to make sure the Pi and debian starts, then flashed it with HA and restored a backup.

Make sure you have a SSD that your Pi can handle (with proper supply) or you have a separate hub to provide enough current.

(Sorry I don’t have the guides to give you today since I left the Pi some year ago)