Instead of IN we can use ANY with arrays casted to enum array, for example:
create table example_table (
--
enum_field example_enum,
--
);
select
*
from
example_table
where
enum_field = any(array['ENUM1', 'ENUM2']::example_enum[]);
Or we can still use 'IN' clause, but first, we should 'unnest' it:
select
*
from
example_table t
where
t.enum_field in (select unnest(array['ENUM1', 'ENUM2']::example_enum[]));