2 yo article about chicken lab-meat in Singapore https://www.theguardian.com/environment/2020/dec/02/no-kill-lab-grown-meat-to-go-on-sale-for-first-time

They mention that their production line uses fetal bovine serum (at the time) but that their next one wouldn't, but it just wasn't complete for the launch.

Apparently they would use a plant based alternative, but I haven't been able to find an article (not behind a paywall) on that.

I wouldn't be surprised if it's a solved problem, imo they wouldn't be able to use fetal bovine serum in large quantities anyway due to it's price.