This Gist has Script to download Debug Logs as a Bulk Jub from Salesforce.

download_all_saleforce_debuglogs.cmd

rem I have modified this Script from a bash script to a Batch Script
rem the modified Bash Script for this was created by roko-p
rem Here is the Git URL for Bash Script Using SFDX-CLI
rem https://gist.github.com/roko-p/d5d519c1cb4addfdd4644fd11c0aaa02

rem Below are the comments by roko-p
rem This Original is a script by Thomas Gagné posted here:
rem https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000A8irTSAR
rem but modified to use the `sfdx` CLI tool instead
rem of the `force` CLI tool.
rem Just add the username
rem (to specify which org to run this against) to both
rem sfdx commands with `-u [email protected]`
rem Original comments below:

rem script for export ALL debug logs to a subdirectory
rem named "log".  
rem it requires the "force" CLI tool be available and
rem assumes the user is already logged in.
rem Sure, I could have added more debugging, like checking
rem to see if the user was logged in, but I didn't have 
rem all night. ;-)

rem 2017-08-29 [email protected]

@echo off

for /f "delims=" %%f in ('sfdx force:data:soql:query -u <username> -q "select id from apexlog"') do ( 
	echo "writing log/%%f.log"
	sfdx force:apex:log:get -u <username> --logid %%f > log/%%f.log
	)

@echo on
echo Log Download Completed