AWS Aurora MySQL Error After Update to 3.05.01

Regarding the error message, I would like to inform you the error "Character set 'utf8mb3' is not supported by .Net Framework" is a client side error and as you mentioned, a mysql bug report is already filed for the same.

[+] https://bugs.mysql.com/bug.php?id=107259

As per the bug report created it states using the connector/NET v. 8.0.32 should fix this issue, however, in some cases this error is still occurring.

After checking internally and consulting with our engineers, there is no standard or recommended fix for this issue provided by AWS RDS as this issue is related to third party software. The fix will be incorporated into the RDS when it has been released by Oracle MySQL in the coming versions.

Therefore, I recommend tracking this bug with Oracle MySQL from below link for updates:

[+] https://bugs.mysql.com/bug.php?id=107259

In order to avoid this error, you may continue to use the MySQL version 8.0.28 or lower.