How can I group together rankings by number of users?
Your data is not enough to give the query a good test, but this FIDDLE seems to do it.

code of dbfille added:

SELECT y.journey, RANK() OVER (ORDER BY cnt DESC) as ranking
FROM 
(
    SELECT x.journey, count(*) as cnt
    from 
    (
        SELECT ID, STRING_AGG(RTRIM(evar),',') as journey
        FROM journey
        GROUP BY ID
    ) x
    GROUP BY journey
) y;


output:

journey,     ranking
content,support,     1
landing,content,homepage,     1
support,content,     1


when I add an extra journey like this:

INSERT INTO journey VALUES 
(4    ,'landing'   ,'2019-01-01',      1   ),
(4    ,'content'   ,'2019-01-02',      2   ),
(4    ,'homepage'  ,'2019-01-03',      3   );


output: 

**journey,     ranking**
landing,content,homepage,     1
support,content,     2
content,support,     2