1. Create a Custom Report type for Chat Transcripts object.

2. Create a report using the report type created from the step1.

3. Create a formula field in the Report to find the hour of Chat Transcript End Time.

Formula:

LEFT( RIGHT( TEXT( LiveChatTranscript.EndTime – ( 4/24 ) ), 9 ), 2 )

Note:

I haveused GMT-4 for the hour calculation. You can adjust it as required.

Reference Link:

https://help.salesforce.com/s/articleView?id=000319411&type=1

Output:

Video Reference: