Add the entry truesdk under LSApplicationQueriesSchemes in into your Info.plist file
<key>LSApplicationQueriesSchemes</key><array><string>truesdk</string></array>
Add the associated domain provided by Truecaller (for example applinks:si44524554ef8e45b5aa83ced4e96d5xxx.truecallerdevs.com) in Your project -> Capabilities > Associated Domains. The prefix 'applinks:' is needed for universal links to function properly.
Important: Replace the 'https://' part from the provided app link with "applinks:". ie https://si44524554ef8e45b5aa83ced4e96d5xxx.truecallerdevs.com
should become applinks:si44524554ef8e45b5aa83ced4e96d5xxx.truecallerdevs.com
while adding to entitlements.
(Note that there is no http:// or https:// prefix when setting up the applinks:)