Комментарии лежат в скрипте в коде страницы
import requests
import json
import re
headers = {'user-agent': 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36'}
r = requests.get('https://www.instagram.com/p/CKJ4986gdbW/', headers=headers)
script = re.search(r'window._sharedData = (.+?);</script>', r.text).group(1)
data = json.loads(script)
edges = data['entry_data']['PostPage'][0]['graphql']['shortcode_media']['edge_media_to_parent_comment']['edges']
for edge in edges:
text = edge['node']['text']
author = edge['node']['owner']['username']
print(author, text)