The canonical solution for this is now on the Snowflake community. - Replace the implicit join of a comma explicitly with JOIN

https://community.snowflake.com/s/article/Lateral-View-Join-With-Other-Tables-Fails-with-Incident

SELECT * FROM 
TEST T
,  -- replace this
   TABLE(FLATTEN(T.A)) F
LEFT JOIN
(
  SELECT 1 AS B
) A
ON F.VALUE=A.B;



SELECT * FROM 
TEST T 
 JOIN -- With JOIN keyword
   TABLE(FLATTEN(T.A)) F
LEFT JOIN
(
  SELECT 1 AS B
) A
ON F.VALUE=A.B;