Is Strider Hiryu manga considered as canon?
Yes, the Strider Hiryu manga is canon.

The manga series was created by the artist group, Moto Kikaku, in collaboration with Capcom. Since Capcom is credited with the game's creation, the collaboration result with the creator is considered canon.

The manga was serialized from May to October 1988, while the first Strider Hiryu game, Strider (CPS-1) was released in March 1989.
The manga serves as an origins story of the lead character Hiryu.

Source: Strider Wikia