I got the same issue after updating to Wp 5.8.1
disabled the JP plugin by writing -old infront of the jetbpack directory through file manager.
The site was accessible again.
Tried installing the plugin from scratch, installing and activating the plugin doesnt do anything – however if you connect it with wordpress it crashes the whole site and get the same error.
I would think Jetpack has a known issue that got detected by the new wordpress feature resulting in this mess.
Leaving jetpack uninstalled for now.