/* 검색 */
@Override
public Slice<Meeting> findByKeyword(String keyword, Pageable pageable) {
    QMeeting subMeeting = new QMeeting("subMeeting");

    List<Meeting> meetings = queryFactory.selectFrom(meeting)
            .where(meeting.id.in(
                    JPAExpressions.selectDistinct(subMeeting.id)
                            .from(subMeeting)
                            .where(
                                    titleLike(keyword)
                                            .or(addressLike(keyword))
                                            .or(contentLike(keyword)),
                                    isOpenOrFull()
                            )
            ))
            .orderBy(
                    meeting.meetingDate.asc(),
                    meeting.registeredCount.desc()
            )
            .limit(pageable.getPageSize() + 1)
            .offset(pageable.getOffset())
            .fetch();
    return new SliceImpl<>(meetings, pageable, hasNextPage(meetings, pageable.getPageSize()));
}

참고자료

Querydsl 서브쿼리 사용하는 방법(select절, where절)

from절 서브쿼리를 아직 querydsl에서 지원하지않나요? - 인프런

QueryDSL from절 Sub Query 가능하게 하기