Sectigo at present offers the ability to cross-sign certificates with the AddTrust legacy root to increase support among very old systems and devices. This root is due to expire at the end of May, 2020. Any applications or installations that depend on this cross-signed root must be updated by May, 2020 or run the risk of outage or displayed error message.
For the vast majority of use cases Sectigo’s standard root supplies the full required client support. For unusual cases, Sectigo offers a new cross signing option with its AAA root.