We too have this problem because the mysql MariaDB Galera Cluster replication works only with InnoDB storage engine, see
https://mariadb.com/kb/en/library/mariadb-galera-cluster-known-limitations/

For now we have manually modified the \application\core\db\MysqlSchema.php file and set the engine option on row 18:

$options = 'ENGINE=InnoDB ROW_FORMAT=DYNAMIC DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci';

Moving to InnoDB will severely limit the size of surveys.

The limit of InnoDB to which you refer, I think it's the maximum number of columns, which if I'm not mistaken is 1017 (vs 4096 of MyISAM). In our case, with about 500 questionnaires (someone very very complex), we never exceeded 400 columns.

In our case with MariaDB Galera cluster we are forced to choose InnoDB, MyIsam is not supported!
IMHO I think that at least it should be given the opportunity to choose the engine when installing LimeSurvey!

PS: If someone else wants to verify, to show the number of column of the tables of your surveys, you could execute this query:
SELECT information_schema.columns.table_name, count() AS Columns
FROM information_schema.columns
WHERE information_schema.columns.table_name like 'limesurvey%'
GROUP BY information_schema.columns.table_name
ORDER BY count() desc

Yes, MyISAM DB column içn real survey is more limited to something around 700/800 with single choice + text question

InnoDB support is now available in LS4