Could you fix this issue, please - [ACJIRA-1596] - Ecosystem Jira, so we can migrate to Jira version 3 API (though, it seems the GDPR changes and the Jira v3 API roll out date are not in sync - API v3 roll-out date? - #2 by yvesriel)
According to our tests we are forced to use v3 API to assign issues to users using accountId - Creating Jira issue with custom assignee in Jira cloud fails with account not found. But because of the open bug mentioned we cannot use it with custom fields / description field