Help with accessing a server via SSH within a university network

Sorry for the long post!

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TLDR: How to access a server via SSH from a PC connected to a different router, but both are within a university network, without getting help from the IT team?

(Note: The PCs and the server are properties of the lab, so we are not hacking or doing something illegal)

A rough representation of the network: https://postimg.cc/LhVm6vZB

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Hi everyone,

I hope my question comes under enterprise networking as it concerns a university.

A little backstory:

I work in a university lab and our internet is provided by our uni. So the IT team of the uni controls which PCs and routers can be in the network.

Little over a decade ago, much before I joined the lab, my boss bought a server for backing up data from PCs used in experiments (Setup PCs 1-3). There are also some legacy scripts in them which connect to the server via SSH to access data from it for analysis. The Setup PCs are connected to separate routers.

Everything was running fine until our uni's IT team recently decided to take the server off the network and forced us to use other network drives. They said that the OS has to be updated, I did that, then they added that the server was out of warranty, and did not cooperate with us further.

My boss is understandably upset because he wants to run some old scripts that use the server, but he cannot do so. He spent thousands of euros to get the server exclusively for our lab, and now when he is about to retire, they are asking him to switch to a new system. Apart from the time spent on setting up the drives and changing the scripts, there is also additional cost for the network drives, which further strains our limited budget. Moreover, I don't see a need to update our server for our purposes. So I was looking for alternative solutions and I put the server behind the router that we use for Setup PCs. I want it to be accessible from other PCs within the uni network, but since the people in our lab and I are not familiar with networking protocols, we ran into a few problems.

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Problems:

• (refer to the image) We can access the server via SSH on the Setup PCs 1 and 2 which are connected to the same router, but we want to access it via the PC 3 on a different floor. We couldn't find out the correct (public) IP for the server because the public IP displayed is that of the uni's main router (or hub? sorry, I don't know the correct terminology).
• I found that port forwarding can be used in the routers to direct SSH requests to the server. But since the routers we use are within the uni network and since we don't have access to the main router of the uni, I am not sure if we can actually do SSH tunneling.
• I tried OpenVPN to make it seem like the PC 3 is in the same router as the server, but the same public IP problem persists, and so the PC 3 couldn't connect to the VPN service running on the server.

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Could someone please guide me on how to solve this? Or even if you could suggest some resources that would help me understand the problem better, it would be much appreciated.

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Please let me know if I should clarify something. Thanks in advance!