Cleaning Up Unused Files to Free Up Disk Space

That looks to me like HA doesn’t like the public key (maybe formatting). Instead of using a USB, I opted to go this route:

So, at step 2, you’ll open the publickey file and copy the contents into the key section under configuration for the Terminal & SSH add-on. Then, use the add-on to run the commands for steps 2 and 3.

I’d also use a password free private key.