As I mentioned before, the hkmap.live app is a good resource for identifying current trouble spots. The notes are in Chinese, but all you really have to know is steer clear of areas with lots of clustered symbols. (Scattered symbols don't usually mean trouble, just the current location of police vehicles.)
It's available for Android and, for the time being at least, Apple.
The Twitter MTR Update account shows MTR status, though it can be a bit hard to follow.
ATMs have sometimes run short of cash. Normally not much cash is needed at all in HK given the acceptance of cards of various sorts. But most taxis don't take cards, and if you want to move out quickly from an area you might have to grab a taxi and pay whatever the driver demands, so best to be prepared and carry at least HK$300-$500.
There's been tear gas in various areas, and some residents are concerned about residues on fruits and vegetables coming from wholesale markets and shops in affected areas. Best to be safe and thoroughly wash stuff you buy.
Last edited by 889; Oct 9, 2019 at 12:11 pm