PART 1
There are some things that must be done in Snowflake before you can set up Microsoft Fabric Snowflake Mirroring. This Tutorial: Configure a Microsoft Fabric mirrored database from Snowflake (Preview) calls out what needs to be done in Snowflake, but not how to do it. If you are missing something in Snowflake, the connection setup will Fail, or you will see something like the attached image where the database you want mirror is greyed out. I'm no expert at Snowflake, but I'm going to share what I'm doing to get this working:
1) Log into Snowflake and create a User in Snowflake Called FABRIC_MIRROR:
CREATE USER FABRIC_MIRROR PASSWORD = 'YourSecurePassword'
2) Then, l created a POWERBI_ROLE:
CREATE ROLE POWERBI_ROLE;
3) I granted some privileges to the new POWERBI_ROLE:
GRANT USAGE ON DATABASE_NAME TO ROLE POWERBI_ROLE;
GRANT USAGE ON FUTURE SCHEMAS IN DATABASE DATABASE_NAME TO ROLE POWERBI_ROLE;
GRANT SELECT ON FUTURE TABLES IN DATABASE DATABASE_NAME TO ROLE POWERBI_ROLE;
4) Then, I granted the POWERBI_ROLE to the FABRIC_MIRROR user:
GRANT ROLE POWERBI_ROLE TO USER FABRIC_MIRROR;