The easiest way off the top of my head would be reinstall and manually design your partitioning so anything that’d benefit is on the SSD and everything else is on the HDD. You might be able to get away with / on the SSD and /home on the HDD, I don’t know what all you have installed or what amount of space Ubuntu requires by default. If you wanna go this route, I’d start your reading here: https://wiki.archlinux.org/title/Partitioning#Partition_scheme
The easiest way off the top of my head would be reinstall and manually design your partitioning so anything that’d benefit is on the SSD and everything else is on the HDD. You might be able to get away with
/on the SSD and/homeon the HDD, I don’t know what all you have installed or what amount of space Ubuntu requires by default. If you wanna go this route, I’d start your reading here: https://wiki.archlinux.org/title/Partitioning#Partition_scheme