You might be better off building a simple virtualization box. Check Ebay, Craig’s List, FB marketplace, etc. For old enterprise/mass use desktops. Often you can find old ass Dell optiplex machines or similar for 50-100 bucks.
Throw in 32-64 gigs of RAM which you can pick up DDR3 or Cheap DDR4 used for like 5-10 bucks a stick. Grab some used drives, toss em in. You’ve got a little server box that you can install a hypervisor on, way more power than a PI, and cost the same or less.
Check out XCP-ng or ProxMox as an open source hypervisor to play with. Lawrence Systems YT channel has a ton of great guides for XCP-ng and I think some for ProxMox too. You could also just install a basic Linux server distro and use KVM or related virtualization software on top. Personally, I use a dedicated Hypervisor, but it’s totally up to you.
My personal home lab is just a 2U box with an old 12-core Xeon, 32 Gig of consumer RAM, and a few TB of HDDs with the hypervisor on a 250 Gig SSD, I can run a half dozen VMs no problem on it.
For my NAS solution, I run a VM of TrueNAS, a FOSS NAS solution that I love and has been fantastic for all the years I’ve used it.
I also run Ubuntu Server edition for my personal media server which is Jellyfin, which also is amazing and works great for me.
I got some cheapo Dell network switch for free from an old tech friend, but you can find equivalent equipment for 20-30 bucks easy online or sold locally. Even basic old network gear usually will allow you to play with things like VLANs and trunking.
Grab some old networking cables from a tech surplus place or store online for patching and practicing cable management/organizing.
PFsense or OPNsense are great open source firewall/routing software you can learn on/practice with.