Maybe that does not arise until you start to troubleshoot 48MP, this link, https://github.com/nckmml/ANXCamera/wiki, suggests Ginko does not yet have written 48MP support.
When it says “flash using Magisk Manager” can I just do this through TWRP?
I won’t comment on https://magiskmanager.com/, the instructions for the latest version are different from some older tutorials, but yes TWRP is involved, the rooting job is not to be underestimated if you did not do it before!
Edit. I never got 48MP working, Open camera does now produce 12 MP images for me. You might check out ideas about ANX and the vendor files in this thread [UnOfficial Build] Q & R | Xiaomi Redmi Note 9 series | MIATOLL (curtana, joyeuse, excalibur, gram)