This video is a quick walkthrough showing the backup and restore process of a database on a SQL Managed Instance with bring your own key and TDE enabled.
Here is the SQL code from the video as a starting point for using the copy only backups yourself.
--Show the database is TDE Enabled
SELECT
db.name,
db.is_encrypted,
dm.encryption_state,
dm.percent_complete,
dm.key_algorithm,
dm.key_length
FROM
sys.databases db
LEFT OUTER JOIN sys.dm_database_encryption_keys dm
ON db.database_id = dm.database_id;
GO
--Backup the DB to blob storage
BACKUP DATABASE [TestDB] TO URL = N'https://yourblobaccount.blob.core.windows.net/media/testdb_backup_2019_07_03_140416.bak' WITH COPY_ONLY, NOFORMAT, NOINIT, NAME = N'TestDB-Full Database Backup', NOSKIP, NOREWIND, NOUNLOAD, STATS = 10
GO
--Show the access to the backup and that it is still TDE enabled
RESTORE FILELISTONLY FROM URL = 'https://yourblobaccount.blob.core.windows.net/media/testdb_backup_2019_07_03_140416.bak'
GO
--Drop the original DB
DROP DATABASE TestDB
GO
--Restore the database!
RESTORE DATABASE [TestDB] FROM URL = 'https://yourblobaccount.blob.core.windows.net/media/testdb_backup_2019_07_03_140416.bak'
GO