Ubigi

Ubigi is owned by Transatel, a company with deep roots in telecom infrastructure owned in large part by Japan's NTT DOCOMO. It sells a data-only eSIM for mainland China priced per gigabyte, giving you flexibility in how much you purchase upfront.

The per-GB pricing model works well if you're uncertain how much data you'll use. You're buying only what you need, no massive packages you might not finish.