I always think that if you are willing to learn "server software", why not step-up the game and go with an enterprise-class server while saving some money?
Really, find yourself a 4-6 years old server and have fun! They can cost less than a modern Intel i7 CPU, although shipping could be expensive.
You do not want a server that doubles down as a desktop, if you do that you are starting on the wrong foot. Take your learning seriously, don't mix server (bare minimum OS) and desktop.
I really like the Dell T410, it is very popular (easy to find used and cheap) and very solid. There are plenty of other options as well.
Go the used server route and you will not regret.... as long as you are really serious about learning about all the stuff you mentioned.
PS: myself I have some Dell servers which serve me great, but nowadays I think I would prefer to buy a supermicro used server because a supermicro chassis can easily be reused for some new machine just replacing the internals but with some Dell/HP/Lenovo servers it is not so easy.