Custom notification ringtones
Default Notification Sound: Textra > Settings > Customize Notifications > Android Settings Button or Notification Sound (select Zedge) > Select a ringtone.
Per Contact Notification Sound: Open Textra (Chat List) > Long Press (to enter multi-select mode) choose the chats you wish to customize > tap 3 dots (top right) > Customize > Notifications > Android Settings button or Notification Sound (select Zedge) > Select a ringtone.