Sophos Community:
https://community.sophos.com/
Sophos XG Firewall blog:
https://community.sophos.com/products/xg-firewall/b/xg-blog
Sophos UTM Blog:
https://blogs.sophos.com/?s=utm&submit=Search
Sophos UTM/SUM Known issues lists:
https://www.sophos.com/en-us/support/knowledgebase/117759.aspx (Official)
https://lists.astaro.com/Known_Issues-UTM-V9.txt (RAW text edition)
https://lists.astaro.com/Known_Issues-SUM-V4.txt (RAW text edition)