Well, after I flashed the mod using TWRP, camera2 api wasn't active and Gcam wasn't working but the image was flipped in my default camera app. So the flip fix worked but it didn't activate camera2 api, so I went into build prop to check if persist.camera.HAL3.enabled=1 (this is how I used to activate camera2 api before) and I was surprised to find two HAL3 code lines, one of them was the one mentioned earlier and the other was new (probably had to do with the mod) persist.camera.HAL3.enabled=0# Enabled Camera2 API
After I found these 2 lines I basically started trying different combinations to see if I manage to activate camera2 API, the one that did it was deleting the line added by the mod (persist.camera.HAL3.enabled=0# Enabled Camera2 API) and leaving the old one active (persist.camera.HAL3.enabled=1) I restarted and it all works now.
I have to mention that there was no exact science behind this...I just tried and maybe risked bricking my device, they say it only works on MIUI 10 so I don't recommend doing what I did.