mysql: retrieve all rows using common table expression

You are selecting from nums which will always return 5 rows.

Select from cte and make left join with nums.

You need 2 CTEs, for the 2 cases of 'Gruberstrasse' and 'Wienerberg' and then apply to them a simulated FULL JOIN (because MySql/MariaDB do not support a FULL JOIN):

WITH
cte1 AS ( SELECT n.name, e.value, 
                 ROW_NUMBER() OVER (PARTITION BY e.value ORDER BY e.id) AS rn
         FROM entries e 
         LEFT JOIN nodes n ON n.id = e.node_id 
         LEFT JOIN attribs a ON a.id = e.attrib_id 
         WHERE  a.name = 'LOCATION' AND e.value = 'Gruberstrasse' AND DATE(ts) = CURRENT_DATE
        ),
cte2 AS ( SELECT n.name, e.value, 
                 ROW_NUMBER() OVER (PARTITION BY e.value ORDER BY e.id) AS rn
         FROM entries e 
         LEFT JOIN nodes n ON n.id = e.node_id 
         LEFT JOIN attribs a ON a.id = e.attrib_id 
         WHERE  a.name = 'LOCATION' AND e.value = 'Wienerberg' AND DATE(ts) = CURRENT_DATE
        )
SELECT c1.name LNZ, c2.name WBG
FROM cte1 c1 LEFT JOIN cte2 c2
ON c2.rn = c1.rn
UNION
SELECT c1.name LNZ, c2.name WBG
FROM cte2 c2 LEFT JOIN cte1 c1
ON c2.rn = c1.rn

Note that applying the condition:

a.name = 'LOCATION'

in the WHERE clause makes your LEFT join actually an INNER JOIN.
If the code works then fine, but if not then you should move this condition in the ON clause.
The same applies for the condition:

DATE(ts) = CURRENT_DATE

if ts is not a column of the table entries.

Before anything, since you're using MariaDB version above 10.1, you're in luck. MariaDB has such a thing called Storage Sequence Engine built-in. This thing can give you as many numbering sequence you want. So instead of doing:

SELECT 1 rn UNION 
          SELECT 2 UNION 
          SELECT 3 UNION 
          SELECT 4 UNION 
          SELECT 5

You can just do:

SELECT seq AS rn FROM seq_1_to_1000;

This will directly give you numbering sequence from 1 to 1000. Of course, you can add more than that and even using some other function than just running numbers. You can refer to the documentation link I've provided above.

The next thing I assume would be, "what if the rows are not even more than 100?". Like that, you don't need to change the numbering sequence but you can add another HAVING function at the end of the query, and maybe some IFNULL in the SELECT to replace NULL with some value.

Maybe something like this:

WITH
cte AS ( SELECT n.name,
                e.value, 
                ROW_NUMBER() OVER (PARTITION BY e.value 
                                   ORDER BY e.id) AS rn
         from entries e 
         LEFT JOIN nodes n on n.id=e.node_id 
         LEFT JOIN attribs a on a.id=e.attrib_id 
         WHERE  a.name = 'LOCATION' 
           AND e.value IN ('Wienerberg', 'Gruberstrasse')
           AND DATE(ts) = CURRENT_DATE
         ORDER BY e.id
       ),
nums AS ( SELECT seq AS rn FROM seq_1_to_1000 )
SELECT IFNULL(t1.name,0) LNZ, 
       IFNULL(t2.name,0) WBG
FROM nums
LEFT JOIN cte t1 ON nums.rn = t1.rn
LEFT JOIN cte t2 ON nums.rn = t2.rn
WHERE t1.value = 'Gruberstrasse'
  AND t2.value = 'Wienerberg'
--  AND COALESCE(t1.name, t2.name)
HAVING (0) NOT IN ('LNZ','WBG')
ORDER BY nums.rn;

Try this if it would work.

EDIT:

Here's another suggestion

SELECT Seq, 
       IFNULL(GROUP_CONCAT(CASE WHEN B.value='Gruberstrasse' THEN B.Name END),0) AS 'LNZ',
       IFNULL(GROUP_CONCAT(CASE WHEN B.value='Wienerberg' THEN B.Name END),0) AS 'WBG'
FROM seq_1_to_1000 A LEFT JOIN
(SELECT n.name, e.value, 
                ROW_NUMBER() OVER (PARTITION BY e.value 
                                   ORDER BY e.id) AS rn
         FROM entries e 
         LEFT JOIN nodes n ON n.id=e.node_id 
         LEFT JOIN attribs a ON a.id=e.attrib_id 
         WHERE  a.name = 'LOCATION' 
           AND e.value IN ('Wienerberg', 'Gruberstrasse')
           AND DATE(ts) = CURRENT_DATE
         ORDER BY e.id) B 
 ON A.seq=B.rn GROUP BY A.seq
 HAVING LNZ+WBG <> 0;

Without using cte:

1. LEFT JOIN the numbering sequence directly with the sub-query you originally made for the cte.
2. Using GROUP_CONCAT with CASE expression in SELECT then GROUP BY numbering sequence - added IFNULL to return zero and use that as filter in HAVING.