I have two labs; one on-prem (lol my home office) and one in AWS. Depending on what you're doing and how "shiny" you want it to be, you can go pretty far in AWS for less than $50/mo (and a little less far for $20). And that comes with the added benefit of haing AWS skills for your resume.

For hosting on AWS, chose services that run well on nano/micro instances. For everything else, run it from home (network policies notwithstanding, see 3 paragraphs down).

Also AWS, if you're setting up a VPC with proper private/public subnetting (and you really should), don't use their NAT gateway. It's WAY too expensive. I set up a NAT gateway on a T3.nano and it costs me $3.74/mo (theirs would have been like $35/mo, which would have blown half my AWS budget on just that). I don't remember if I used this specific article as a guideline, but he did exactly what I did (specifically the iptables config), so I'm confident in pointing you to him.

As for on-prem; look into Beelink's offerings. I just got two of their miniPCs ( specifically these ) for $150 total (on sale) and will be moving some of my heavier stuff (matrix, fediverse) from AWS to these. You don't need these specific ones, check their store, it has a section for models on sale, find something you like and get it cheep.

Now, I know you can't host anything on their network that would touch the Internet, but something like these would be great for self-hosting Plex/Jellyfin, or other services that are technically only local, but also still technically on the network (hell, you don't even need their network; buy a second-hand Netgear router and make your own private network). Those mini-PCs would also be great for learning linux, since you said you can't really run VMs. if you want to learn about general self-hosting (web services like Apache/nginx, get a little PHP or Python site going, etc) you can do that totally locally on your private network, and it'll be the same experience as doing it in the cloud (except no one but you can see it, but hey, everyone needs a "dev" environment; Cloud can be "production" if you want an audience).

Hope this helps!