I haven’t seen it just flat out break the browser like that. I have had bugs and issues with the extension in the past, which is why I switched to the Windows app. My first guess would be un-installing and re-installing the extension.
If that doesn’t work, the app does have “Inverse” split tunneling, where only the listed apps and IPs go through the VPN, nothing else will. It’ll have the same effect as the extension.
The CEO 6ish months ago, ignorantly tweeted an approval of a specific Trump appointee. So a few now believe Proton to be ride or die MAGA. Which is silly, considering it’s a Swiss company run by scientists.