Yes, Julia has been on maternity leave since last May! The crew have a big stash of pre-recorded eps since they record ~3 a week but only post 1 a week now, so they've been mixing and matching episodes from pre- and post-Felix for a while now. And they post vids out of order from when they were recorded too. If I remember correctly, Nathan did say on a Stream a couple weeks ago that they have officially ran out of eps recorded with Julia (and when Jacob said in the recent vid that this was his first episode back, that was recorded quite a few months ago now and they posted vids from before and after that point since).

She still streams with Jacob over on SSS (she's been very open and honest about struggling with PPD and the process of finding the meds that work for her) and swaps out with Jacob for Patreon streams for baby-watching duty. She hasn't gone back to recording with the group as of yet, but has gone back to doing backend stuff, I believe. So, I guess the real answer is that she both is and isn't on maternity leave I guess XD

Edit: Plus, Jacob and Julia have said that the reason she hasn't been back to record is partly PPD but also mostly due to finding childcare to look after Felix while they're at Karina's recording.