You may want to educate yourself before spreading unnecessary FUD. Firefox is free and open source, and always has been. There's no danger in Firefox becoming a paid browser because even if they tried, it would just be forked and maintained by another community or group.
Mozilla does have a for-profit arm called the Mozilla Corporation, and they manage the money received from Google and others. But that doesn't mean Firefox is going to become paid even if Google gets broken up by the antitrust efforts of the US government.
There are already other open source forks of Firefox that are community driven and maintained without employees or a for profit organization behind them. The obvious example is LibreWolf which describes itself as "a custom and independent version of Firefox, with the primary goals of privacy, security and user freedom". There's no argument that maintaining a web browser is currently complex and needs to make security first decisions, but LibreWolf as an example shows us that it is not only possible but I argue proves it will continue even if Firefox as we know it goes away.