For CLI, diff has already been mentioned; for a GUI application I'd recommend meld:

https://meldmerge.org/

Work (Datacenter): RHEL, some SLES

Desktop: Kubuntu (just works, more or less - start with minimal install to avoid snaps)

Steam Deck: runs arch btw

Thanks a bunch that's good advice - I'm actually responding from Beijing right now.

It looks like all major esim providers with a dedicated plan for China (nomad, saily and many others) should work fine. Just compare for a moment and choose the one with the best offer (most data for what you're willing to pay) at the moment. Make sure to edit ASP if it doesn't connect at first.

And yes, cash seems definitely dead and buried around here. I found alipay maybe a little less painful to setup than WeChat, but YMMV and the latter provides chat functionality which might be useful when communicating with locals.

Thanks again for your help!