See for example the contemporaneous polling done by Reuters below - 59% of the population supported the protests at the end of 2019 and 30% had participated [1].

I looked into this source.

First, it was commissioned by Reuters, a news agency based in UK.

  polled in a survey conducted for Reuters by the Hong Kong Public Opinion Research Institute

Second, Hong Kong Public Opinion Research Institute had a CEO who was pro-succession, anti-Beijing views and has since been exiled to UK.

Personally, I wouldn't call this survey unbiased.