The Directorate of Minorities Department in Karnataka issues the Linguistic Minority Certificate.The Tahsildar of your concerned district is the authorized person to receive applications and issue the certificate.

• Application form duly filled and signed.
• Two passport-size photographs.
• Proof of residence (Ration card, Aadhaar card with address, etc.).
• Proof of identity (Voter ID, Aadhaar card, etc.).
• Proof of belonging to the Linguistic Minority community (This could be a caste certificate specifying the community, a school leaving certificate mentioning the medium of instruction as the minority language, an affidavit from a gazetted officer)
  
  I hope it helps!