While the OS only needs 15-25gb max, what problem are you trying to solve by providing it a smaller partition? If you aren't very experienced with Linux there will be some gotchas you aren't anticipating by sizing it so small. This recommendation doesn't take into account your docker utilization, and keep in mind that docker stores its data under /var/lib/docker. Mine is currently around 25GB from all of the containers I run. I also keep my volume mounts under /docker and that is currently using around 47GB with Plex using 30GB for my 16TB library. If you decide to do virtualization, it's going to end up under /var/lib as well by default.

Like /u/Kiziang, I use the default partitioning and give the OS the full drive. I think the recommendation makes more sense when you're talking about desktop Linux systems, but I haven't done that since like 2011. There are plenty of arguments for doing it either way. Unless you are doing a lot of work in your home directory, do you really need it on its own partition taking the majority of your storage?