Whether you choose to trust them or not, they have a history of publishing content that is false and serves to advance and protect Russia's interests.
One such example on the Skripal poisoning: https://www.rt.com/news/452946-skripal-anniversary-truth-nov...
If you want you can read more about RT and Sputnik here: https://www.kcl.ac.uk/policy-institute/research-analysis/wea...