Microsoft Roadmap
The main place to find updates is using Microsoft Roadmap, it’s fairly accurate and gives you information on what’s in development, rolling out and what has lauched.
Roadmap Radar from Collaboration Coach
Collaboration Coach are producing a new video every month with news from Microsoft 365 Roadmap, mainly focus on Microsoft Teams.
Tech Community
Microsoft has it’s own tech community, this forum is a huge resource for anything Microsoft related. Engage with some of the best people in the world to get answers to your questions and information about features.
UserVoice (discontinued)
UserVoice used to be the feedback portal for Microsoft apps, you would be able to request and vote for features. Microsoft has announced that they will discontinue this and change to an inhouse solution. More information to come.