For your OS > Never ubuntu, use raspberry pi os
For raspberry pi os, install raspberry pi os 64 bit lite ON MICRO SD CARD, if you have SSD, just save them for you docker container config.
After you install the os and update them and restart them do this >
sudo nano /boot/config.txt
add at the bottom >
dtoverlay=disable-wifi dtoverlay=disable-bt
save and restart
With that you block wifi and bluetooth, i don't know why but help for stability for my server (before disconnect from ethernet every day)
if you want to mount your ssd ou disk on you machine >
format disk with >
list disk > lsblk --fs
in my case sda is my disk sudo mkfs -t ext4 /dev/sda
now i create folder where to mount the disk : mkdir /home/pi/mysuperdisk
sudo nano /etc/fstab
add this line at the bottom
UUID=find them with lsblk --fs /home/pi/mysuperdisk ext4 defaults 0 2
save and reboot and good