

The easiest offsite backup would be any cloud platform. Downside is that you aren’t gonna own your own data like if you deployed your own system.
Next option is an external SSD that you leave at your work desk and take home once a week or so to update.
The most robust solution would be to find a friend or relative willing to let you set up a server in their house. Might need to cover part of their electric bill if your machine is hungry.
Given that this is a laptop we’re talking about, OP is definitely over selling it. Bring a backpack, unpack the laptop box into your backpack (assuming the box is too big to fit in the backpack itself). Something bigger like a TV would be more problematic.
The main worry is that being seen with new-in-box fancy electronics makes you look like “guy with money”. It’s not so much that someone’s gonna steal your TV on the subway, but if you can afford a new TV your wallet probably has good stuff in it. Then it’s just a question of “how bad is the crime actually on this commute?”. Most places it’d be fine but some rough parts of some cities I’d be worried.