Metamask-extension: newBlockHeaders subscription is broken

[anxolin]

Describe the bug
Issue subscribing to the block headers event (newBlockHeaders) after updating to Metamask 8
https://web3js.readthedocs.io/en/v1.2.9/web3-eth-subscribe.html#subscribe-newblockheaders

To Reproduce (REQUIRED)

1. Install Metamask for Firefox v8.0.1
2. Go to https://codepen.io/anxolin/pen/RwrxOrK?editors=1111
3. Press connect
4. Press subscribe

Expected behavior
I expect to be notified on every block, like the in the following output.

This output it's taken from the codepen above, using Metamask for Chrome v7.7.9

Screenshots
I don't receive the event notification.

This is the output in Metamask for Firefox v8.0.1:

Browser details (please complete the following information):

• OS: MacOS
• Hardware Wallet: N/A
• Browser: Firefox
• MetaMask Version: 8.0.1

Additional context (Error Messages, etc.)
N/A

[alfetopito]

Adding that I see the same behaviour on Firefox 78.0.1 (64-bits) on Linux with Metamask 8.0.1.