Well, I was lucky. No one cared.
To be safe, I didn't take my laptop with me. But no problem at the border, neither in HK nor in China. I'm just not important enough. Nobody tried to check my phone for social media accounts.
China really sucks for foreigners now, though. Without my friends, I wouldn't have been able to do anything there, because my VPN (PIA) & my eSim didn't work. In Dongguan, you can't even hail a cab anymore. Almost everything is done via ride-hailing apps.
Paying cash in supermarkets or for street food was no problem, though.