Shower Waterproofing

Hello! First post after signing up, I have been reading through the forums and have also watched several of your videos. Thank you for any help. I am working on a shower project and have completed getting the framing plumbed up, rough plumbing is done, and backerboard installation complete. I placed my vapor barrier and metal lath down today. Here is what it looks like currently:

I thought I was ready for the deck mud but am hesitant now after doing more research. Hoping to find some solid answers here:

1. I bought 209 Floor Mud from Laticrete at the local tile store. However, I'm reading on their website that concrete is the only suitable substrate. Recommendations?

Going to apply the multimax lite on the seams and mesh tape next! 😀

Thanks in advance!