I (ubuntu noob) want to assist the network by setting up a Bitcoin node on a Raspberry Pi, but Ubuntu has other plans.

Prerequisites:
* Raspberry Pi 5
* 64GB SD Card
* Ubuntu Desktop LTS 24.04
* Kingston external USB disk 1TB

I have:

1. Installed Ubuntu desktop on my Pi 5, and "sudo apt update && apt upgrade"
2. Verified that the Kingston disk can be accessed via the 'file manager' in Ubuntu.
3. Installed 'Bitcoin-core' (v 27.0) via the Ubuntu app store.

When I click on the Bitcoin node app, I get a prompt (see screenshot) which says 'Approximately 12GB of data will be saved in this directory', and 'when you click OK, an additional 600GB of data will be downloaded', which I don't have space for on the SD card. Therefore, I want to point to my 1TB external Kingston disk, but this is my problem. It's not possible to point to the external disk (which I otherwise access via the file explorer without any issues).

I found a bitcoin-config file which was empty. I tried to add:
datadir=/media/username/KINGSTON but then I can not even start the Bitcoin app without getting error "Settings file could not be written"

What is wrong? Why can I not use my external drive?

(will not answer in DM)

https://preview.redd.it/wnn5oj3h37xc1.png?width=2476&format=png&auto=webp&s=79b3bc05707e157d1df2bb25992dcf51dbe2c593