You can use your home SIM card and enable international roaming. As your data is routed through your home carrier's servers in your home country, it bypasses Chinese restrictions. This is legal but often very expensive ($10–15 USD per day or high per-MB charges).
An important distinction: Hong Kong and Macau operate under the "one country, two systems" framework. WhatsApp works normally in both territories, just as it does in most other parts of the world. A traveler can be video calling from a rooftop café in Hong Kong one moment, then cross into mainland Shenzhen and watch their WhatsApp connections fail entirely.
While WhatsApp groups are the standard for the West, China runs on WeChat (Weixin). If you are looking for local community groups, you won't find them on WhatsApp.
Some research highlights how WhatsApp groups are used within China for specialized, secure communication by groups who require encryption not offered by local apps like WeChat. Gender-Based Violence & Safety : One significant study discusses how a WhatsApp group in China