I want to link Cloud storage like Dropbox or Google drive (or other alternatives) directly to android phone storage folders like Apps, media in order to save media files to cloud storage instead of phone storage. Is there a way to achieve this?
Without root access you cannot make cloud storage available globally i.e. to all apps on device. However, many file explorers (including MiXplorer) support remote storage access just like if it's locally available.
If you have root access you can use
rclone mount which mounts a remote cloud storage using FUSE. All apps can see the mounted filesystem if proper permissions are set. E.g. to mount Google drive:
~# mkdir /sdcard/GDrive ~# nsenter -t 1 -m rclone mount GDrive: /mnt/runtime/write/emulated/0/GDrive --gid 9997 --dir-perms 0771 --file-perms 0660 --umask=0 --allow-other
All apps with
WRITE_EXTERNAL_STORAGE permisison will be able to read/write files to GDrive directory. For details on permissions see How to bind mount a folder inside /sdcard with correct permissions?