[solution] Mount large sdxc tf card with fat32 file system on android 10 - Moto G 5G Plus Guides, News, & Discussion

MicroSDXC card(tf card) usually starts from 64GB memory and it is formatted with exfat file system.
It is fine in most cases but maybe does not play around with IP cameras.
Some IP cameras format SDXC cards with fat32 file system and on this phone (moto g 5g plus with stock android 10) it is not compatible and can't be read (alarm:need format first).
Take my new SDXC card with 64GB memory which will be used on IP camera for example.
IP camera is using camhi/camhipro software and always formatting tf card with fat32 file system.
The tf card then is compatible with Windows and android 7, but not on this phone with android 10.
If you put tf card with exfat file system back on IP camera, the camera will format back to fat32.
So there is dead end for my g 5g plus with an otg usbcard reader or directly insert to easily access the recorded videos.
The need that directly read the recorded video is that the software on IP camera (both itself on android and on Windows)doesn't support multiple playback speed nor multiple download videos through wifi/self-hotspot.
So that's a painful to review recorded videos.
But if you can get direct recorded files, on android, mxplayer can play on 4X speed (although no audio...).
On g 5g plus with stock android 10 , it is only supported SDXC card with exfat file system and even with 16GB tf card formatted with fat32 is not compatible with IP camera that also formatted with fat32.(ouch...)
But on an older phone with android 7 , the android 7 will format SDXC 64GB with fat32 and also compatible with that formatted with exfat.
Doing some search get back few the same situation.But android is like linux , already got phone rooted, there should be a way.
And finally a solution has been found.
1. take off the SDXC card from IP camera and insert it to otg usbreader.
2. plug otg usbreader to the phone and ignore the alarm and DON'T do anything .
3. open termux , type su , type blkid .
You'll see the last line something like:
/dev/block/sdg1: UUID="F7E2-E7B3" TYPE="vfat"
remember the "/dev/block/sdg1".
4.open total commander , add new button , send shell command , su
parameter :
umount /mnt/expand
mount -t vfat -v /dev/block/sdg1 /mnt/expand
(where "/mnt/expand" is the mount point , you can change it to some other new folder like /storage/emulated/0/sdcard . Then you can add this folder as new bookmark or place for quick access.)
5.hit the new button , now you can access the SDXC card that with fat32 file system. You can directly play videos using mxplayer or copy them into internal memory then play afterwards.
6. after things done , disconnected the otg first ,then leave out the mount folder, then hit the command button again .(to avoid "/dev/block/sdg1" path change)
Afterwards, you can just plug in otg , hit the button, go to the mount folder , copy or review , disconnected the otg , leave out the mount folder, hit the button , done.
update1:
The mount point is better to set subfolder below /storage/emulated/0/ to avoid mxplayer failed to play the videos that copy from internal storage to otg usbsdcard.