How do I migrate translated content?
I have found that there is some translated nodes have the same
nid vid only langcode is different


When using translation, that's ok and normal.

However, what's never ok and not normal:

Duplicate entry '8a7e1ba8-9b75-4813-80d6-99104c82efa5' for key
'node_field__uuid__value': INSERT INTO {node} (&quot;vid&quot;, &quot;type&quot;, &quot;uuid&quot;,
&quot;langcode&quot;)

Universally Unique IDentifier cannot be the same, has to be unique. The error is telling you that you have two or more nodes, in the node table, with the same UUID.
So either you have 2 or more Nodes in D8 with the same UUID or perhaps you have a node that was already migrated to D9, but your migration is failing to see that and skip it.
If both are on D8, when you find which nodes have the same/duplicate UUID, via Drupal delete one and re-create it. Just in case, check that the other one didn't get deleted as well because it had the same UUID.