Some considerations as MM3 replacement.
Large screen phones:
Oukitel K9
Huawei Enjoy 9 Max
Huawei 8X Max
Huawei Y Max
Huawei Note 10
Huawei Mate 20
Note the different charging rate, Pixel density ppi and notch.
Oukitel series have the best charging 5V/6A, but slower P35 cpu (SD625 equivalent)
http://www.oukitel.com/products/k/oukitel-k9-112.html
If looking for big battery but don't mind the smaller screen, 6.3" Umidigi S3 Pro or Oukitel K12.
S3 Pro is *enhanced* in every way except for the screen, more expensive also due to beautiful ceramic body and Sony imx cameras. Umidigi F1 and F1 Play is also large battery 5150mAh, compete with Redmi Note 7.
K12 is 5v6a charging 10000mAh, also Sony IMX
https://www.umidigi.com/page-umidigi_s3pro_overview.html
http://www.oukitel.com/products/k/oukitel-k12-114.html
Xiaomi is foolish to leave a vacuum after MM3, this will drive MM fans to other brands. Theres no similar models to offer MM fans from current Xiaomi lineups. CC series and K series not planned since last year and disrupted new products lineups, end up sacrifice MM series.
Samsung A70 is AMOLED, MM3 is IPS LCD. oled have flickering issues but no proper full hardware DC Dimming in place, not even from Oppo Vivo OnePlus or Xiaomi.
Current dc dimming is just software implementation, not good for migraine or sensitive eyes. At low brightness, all color accuracy run road. This is a real and suffering issue.
Consider properly before switching to oled. Current flickering issue is due to oled want to save cost but sacrifice our eyes, causing splitting headache and back of eyeball soreness, even hours after stop using the phone.
To phone makers, our eyes and sanity are cheap.