This error is related to your server; the database has lost connection, and it's not related to your updates.
Please contact your server's support to address the unstable database connection issue.
I checked with the hosting provider. They said, Your site generates a query that slows down the site on every visit and since it's popular, it causes MySQL to slow down and eventually go down. Please advise me.
I will double-check for you, but the hosting provider's response seems to be inaccurate. This is a template that many people use, and the issue only appears on your site.
Can you please check the extensions after the update?