The process for setting up LO to allow typing in a script that differs from the language of the install is a multi-step one that requires:
- Install of LO language pack e.g., the DEB package for x86_64 architecture for Hindi (hi) and Malayalam (ml) can be found here.
- Install of a supporting font.
- Selecting of a keyboard layout.
- Use of an input method (in some cases).
- Configuring LO language settings.
- Selecting of the default font to use in LO.
I indicate the basic process in my answer here for Telugu under Fedora. The basic LO language settings required for Hindi are outlined in my answer here but please note the answer beneath this for selecting the required keyboard layout. Step #4 is sometimes also chosen by people who require an alternate input method (e.g., I-Bus).