For S7 Basic economy fare, only hand baggage is included.
As a OW Emerald member, do I get one piece of check-in baggage for free?
OW extra baggage allowance
https://www.oneworld.com/ffp/extra-baggage-allowance
The following website only mentions about S7 elite members.
https://www.s7.ru/home/info/baggage.dot
Thank you.