I don’t know about today’s fabrics, but back in the day, I used to make a small cut, about 1/2” long into the selvedge edge of the fabric and rip it to the next selvedge. You can then follow the tear for a straight edge.
Cheaper fabrics might not be straight, so fold the fabric in half cross-wise to see if the edges and corners meet before you tear. Just remember that however the fabric leans is how your article will lean after the first washing.
Yep, rip it.