Not able to set utf8mb4 character collation, running into encoding issues with emojis.

Dear community, after a database migration we face serious issues in the production system, and I hope you can help me quickly!

We face issues with storing emojis and other special characters in our MySQL database. We get the following error:

Conversion from collation utf8_general_ci into utf8mb4_unicode_520_ci impossible for parameter

prisma:query INSERT INTO `app`.`show` [...]
PrismaClientUnknownRequestError: Error occurred during query execution:
ConnectorError(ConnectorError { user_facing_error: None, kind: QueryError(Server(ServerError {
   code: 3988,
   message: "Conversion from collation utf8_general_ci into utf8mb4_0900_ai_ci impossible for parameter",
   state: "HY000" })) })
at cb (/app/node_modules/@prisma/client/runtime/index.js:38695:17) { clientVersion: '3.8.1' }
prisma:query ROLLBACK

Our MySQL cluster has utf8mb4_0900_ai_ci set as default on all levels (db, table, column) but Prisma still sends utf8 (utf8mb3) to the database. How can I configure the charset of the underlying mysql-client/connection?

I tried SQL_PRISMA_URL='mysql://user:pass@host:port/db?charset=UTF8MB4&sslmode=require&sslcert=ssl.crt&sslaccept=accept_invalid_certs' but the charset argument gets ignored. It is also not listed as an argument which is passed, so I wonder how I can specify it. Here is the docs: https://www.prisma.io/docs/concepts/database-connectors/mysql#connection-details

Querying await prisma.$queryRaw(SHOW VARIABLES LIKE 'character_set_%') returns

• ‘character_set_client’: ‘utf8mb3’
• ‘character_set_connection’: ‘utf8mb3’
• ‘character_set_database’: ‘utf8mb4’
• ‘character_set_results’: ‘utf8mb3’
• ‘character_set_server’: ‘utf8mb4’
• ‘character_set_system’: ‘utf8mb3’

Which shows that it is a Prisma mysql-client/connection issue – I guess?

Thanks for help! Florian