CB

Based on the default_language language files I created an English test language plugin that has all strings prefixed with an exclamation mark (!).

This reveals many untranslated strings.

I have attached the test language plugin for replication purposes.

Here is an initial list of identified issues:

On Admin menu drop-down the following elements are not translated:

Tools
Configuration
Add New User
Add New Tab
Add New Field
Add New List
Install New Plugin

On the Configuration page the following elements are not translated:

General (tab name)
Connections (tab name)
Integrations (tab name)
Username and None (Login Method dropdown options)
Field icons (label and tooltip)
Name (on Username fallback option)
Template (label)
Rest
Yes / No (Maintain Aspect Ration options)
No (Allow Moderators to Edit option)
None, Email, PMS (on Notification method dropdown)
No (on Translation highlights options)
Automatic (on Version checking option)

On User Management page:

New, Edit, Delete buttons in toolbar
Name, Username, Group, Banned columns
Select Group in Search Tools
Select Operator in Search Tools
Search and Process buttons
Send Mail and Cancel buttons in Mass Mailer area
Editor and Group labels in contact info tab (I guess these are picked up from Joomla)

On Tab Management page:

Title, Description, Display, Plugin, Published, ID columns
Global tab during edit
Publish label during edit

On Plugin Management Page:

Name, Version, Published, Type, ID in column titles