Only teachers with teaching certificates will be allowed to teach in China

May I share an update: The Chinese Ministry of Education has this announcement. Starting from Jan 1st, 2020:

School-age students located in mainland China will be unable to take any type of classes after 9:00 p.m. (Beijing Time).

Only teachers with teaching certificates (TESOL etc) will be allowed to teach in China, in-school or online.

Do understand that any company operating around these may not exactly be legitimate, and we know what happens if we get in trouble with companies that are not legit. You may not be entangled in their laws but it will be hard to chase after companies that are illegal, to begin with.