I think the only closed-source extension I run is lastpass, and I'm evaluating open-source alternatives.
How do people who cannot read code even cope, I don't know.
I deleted my account and switched to BitDefender. Still getting the LastPass emails though, whenever I check my spam folder.
Also, LastPass slowed my Android phone a lot. BitDefender doesn't seem to do that.
In short, my recommendation is: stay the hell away from LastPass. They can't even handle an email system, I don't trust them at all to handle my passwords.
Their Windows application was also painfully slow.
I paid them for years but I no longer trust them, it seems to me they are incompetent as an organization even if the people who work there might or might not be smart.