It worked with DBeaver! Thanks.
For what it's worth, DBeaver popped up this message, "SQLite driver files are missing."
So I downloaded the drivers using DBeaver.
Like you said, I used the full path to the location where I downloaded the .DLL (64-bit):
SELECT load_extension('C:\SQLite\Windows64\stgeometry_sqlite.dll','SDE_SQL_funcs_init');
Then, as the docs suggest: "Call the CreateOGCTables function to add ST_Geometry tables to the database."
SELECT CreateOGCTables();
Now, I'm able to run SQL queries that use ST_GEOMETRY functions on the mobile geodatabase:
SELECT objectid
FROM (SELECT ply.objectid,
row_number() over(partition by ply.objectid order by null) rn
FROM ply
CROSS JOIN pnt
WHERE st_intersects(ply.shape, pnt.shape) = 1
)
WHERE rn = 1
Query source: Spatial Query Benchmarking
Ideas: