Using server version 10.5.8-MariaDB-1:10.5.8+maria~stretch mariadb.org binary distribution
with ColumnStore storage engine PLUGIN_AUTH_VERSION 5.4.1-Stable one can get

CREATE TABLE t1(test varchar(2667)) ENGINE=Columnstore DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.328 sec)

However, with later releases
Server version: 10.5.9-MariaDB MariaDB Server
or
Server version: 10.5.10-MariaDB-1:10.5.10+maria~stretch mariadb.org binary distribution
the command above fails:

CREATE TABLE t1(test varchar(2667)) ENGINE=Columnstore DEFAULT CHARSET=utf8;
ERROR 1815 (HY000): Internal error: CAL0009: (3)Create table failed due to char, varchar and varbinary length may not exceed 8000

Only lower length works:

CREATE TABLE t1(test varchar(2666)) ENGINE=Columnstore DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.299 sec)

Also the error message looks confusing, since attempt to use varbinary in 10.5.10-MariaDB

create table t1(name varbinary(800)) engine=Columnstore;

results in

ERROR 1178 (42000): The storage engine for the table doesn't support Varbinary is currently not supported by Columnstore.

and the char length can't exceed 255:

create table t1(name char(256)) engine=Columnstore;
ERROR 1074 (42000): Column length too big for column 'name' (max = 255); use BLOB or TEXT instead