Unknown collation or Unknown character set
This usually means that there’s a database version mismatch.
WordPress supports lots of versions of MySQL and MariaDB database servers, and so we offer many different versions on our staging servers to get the best match for your website’s database. However, with the hundreds of different reported client versions, in rare circumstances a staging site ends up on a staging server with a mismatched database version, which will result in this error. This is easy for us to fix if you report it to us, and we can update our routing process to make sure it doesn’t happen again.