I suppose it comes down to: How important is it that you not pay for the suite you’re using? If it is important, then there are several options that will work (with varying levels of compatibility with Microsoft documents), including Apple’s apps, Google’s web-apps, LibreOffice and others.
If, however you feel that using the actual Microsoft suite is important, I think the pricing is pretty reasonable, even though it won’t come close to your university’s pricing.
And one nice thing is that if you install Microsoft 365 via your university (using the university’s Microsoft ID) and you later want to switch to a personal/family subscription, you don’t need to reinstall anything. Activate your subscription, then sign out from your university ID and sign in to your personal ID and it will just continue working.
Are you doing anything where you think it might matter? And what version of macOS is it currently running?
I never had any problems with Catalina, but in my case it came pre-loaded on a 2018 Mac mini. The biggest potential concern for you is that Catalina drops support for 32-bit apps. If you have any you need to run, you’ll need to upgrade them. In my case, the ones I had to pay to upgrade were Photoshop Elements and FileMaker. Everything else I could either upgrade for free or just abandoned (but didn’t delete in case I decide to set up a VM to run them on).
Another possible concern might be moving from iTunes to the decentralized suite of Music, Books and Podcasts, with sync running via the Finder. For me, there weren’t any major problems (aside from a one-time glitch during system migration), but you should note that Music doesn’t support Internet Radio the way iTunes did. If you use that feature, you’ll need to get a different app.
(I don’t know if an upgrade will force you to migrate over or if you can keep using a pre-installed iTunes. I suspect it will depend on whether iTunes is/was 32- or 64-bit. In my case, it was migrating to a new system, so I didn’t have that option.)
If you were making bootable backups with Carbon Copy Cloner, you can continue to do so with Catalina, but the boot system did change to separate system/data volumes, so your backups will be different. I would recommend wiping your clones and starting fresh (or get new drives if you want to keep your older backups). The issues that make it difficult to produce a bootable Big Sur (and later) backup shouldn’t affect Catalina.