Tuta (previously Tutanota) because it’s private, runs on 100% renewable energy, very affordable if you want to use a custom domain, has end-to-end encryption between Tuta emails and it’s email clients are open source including a very nice app on F-Droid
If you really need a computer and don’t have the budget for one that costs $600, then don’t get a $600 computer. There are plenty of old office PCs on eBay that you can get for less than $100 and they should be fine for only homework. Just search for “Office PC” on there. This is not the place to be asking for money, but I hope you find something that fits your budget and that university goes well.
I saw this and thought “How is this even possible? No way you run an SSH server from initramfs…” Turns out that’s exactly how you do it, I’ll be trying this out thank you!