The show is about wrestling and takes a long time to film, so the report (also Deadline) indicates that the earliest we would have even gotten a fourth season given the current climate and filming conditions would be 2022.
COVID-19 is being cited as the reason for the lack of a final season with Glow, which makes sense in a lot of ways.
Either way, Teenage Bounty Hunters’ cancellation does not explain Glow.
Apparently, the show didn’t have “glowing” enough feedback to be worth the wait, particularly given costs are rising on movies and TV productions alike given COVID-19 testing and other safety precautions.