Blitz Hub is one of the most reliable WoT Blitz news and leak Discord communities/Youtube channels.
News of upcoming game content such as new tanks, game features, etc, is regularly posted by Blitz Hub (some examples below).
BlitzHub also occasionally posts quick and concise tank reviews on Youtube, and some event guides.
Blitz hub has multiple different language channels, you can access them here:
BlitzHub EN/EU Discord server
BlitzHub RU/CIS Discord server
BlitzHub English language Youtube channel
Blitzhub Polish language Youtube channel
Blitzhub Russian language Youtube Channel
Below are some examples of the news and leaks that are posted by BlitzHub on the Youtube channels.
GuidesBlitz 