How to lock Metamask to Ethereum mainnet?

I have a website with a payment button. It launches Metamask with it locked to a specific payment address, contract address, and payment amount. Is there a way to also lock it to the Ethereum mainnet?

Apparently users are dabbling with BSV or Matic, and not realizing that they’re still set to those networks, which causes problems.

I googled the issue and found ChainId as a parameter, but it appears to be depreciated or ignored.