Found this from https://andyatkinson.com/speaking-opportunities and Cybertec https://www.cybertec-postgresql.com/en/get-rid-of-your-unused-indexes/

unused-indexes-timescale.sql

SELECT s.schemaname,
       s.relname AS tablename,
       s.indexrelname AS indexname,
       pg_size_pretty(pg_relation_size(s.indexrelid)) AS index_size
FROM pg_catalog.pg_stat_user_indexes s
   JOIN pg_catalog.pg_index i ON s.indexrelid = i.indexrelid
WHERE s.idx_scan = 0      -- has never been scanned
  AND 0 <>ALL (i.indkey)  -- no index column is an expression
  AND NOT i.indisunique   -- is not a UNIQUE index
  AND NOT EXISTS          -- does not enforce a constraint
         (SELECT 1 FROM pg_catalog.pg_constraint c
          WHERE c.conindid = s.indexrelid)
  AND s.schemaname NOT LIKE '_timescaledb_%' -- ignores hypertables and caggs
ORDER BY pg_relation_size(s.indexrelid) DESC;