I have already installed ubuntu 24.03LTS and works ok in Raspberry Pi 4.

Now I want to install Ubuntu in a Raspberry pi 5 which has two USB sticks in its USB3 port and it supports boot from USB.
How can I have an installation with custom partitions that will be md RAID as I do in x86 hardware?
I want to have Ubuntu OS in two RAID 1 partitions for / and /var directories and probably for /boot/firmware also.