SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
WHERE 
  cscart_products_categories.product_id IN (
    104, 376, 390, 511, 512, 513, 514, 1612, 
    1613, 1614, 1615, 1616, 1617, 1618, 
    1628, 5476
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00370

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "pt",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 464,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (104,376,390,511,512,513,514,1612,1613,1614,1615,1616,1617,1618,1628,5476)"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "c_status"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "ref": ["herbaria_cscart_4_18.cscart_products_categories.category_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "cscart_categories.storefront_id in (0,1) and (cscart_categories.usergroup_ids = '' or find_in_set(0,cscart_categories.usergroup_ids) or find_in_set(1,cscart_categories.usergroup_ids)) and cscart_categories.`status` in ('A','H')"
    }
  }
}

Result

product_id category_ids
104 304,242,241,89,85,77,70,69,67,55,52,31,306,229M
376 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
390 306,258,23,261,242,82,70,68,67,56,28,27,269,1M
511 304,242,241,89,85,77,70,69,67,55,52,31,306,229M
512 304,242,241,89,85,77,70,69,67,55,52,31,306,229M
513 304,242,241,89,85,77,70,69,67,55,52,31,306,229M
514 304,242,241,89,85,77,70,69,67,55,52,31,306,229M
1612 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1613 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1614 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1615 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1616 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1617 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1618 242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,336,29,1M
1628 306,258,23,261,242,82,70,68,67,56,28,27,269,1M
5476 336,242,307,306,304,271,270,261,258,234,233,222,217,208,194,181,104,101,95,94,91,88,82,79,71,70,67,56,49,42,41,23,17,15,10,29,1M