Thanks for reply! The modsecurity package is an example. You can do the same for steps for brotli, you need to create a custom startup.sh file and add the steps for brotli install in that script. You can then update the startup command in portal to point to startup.sh
You may follow the steps here: How To Enable Brotli Compression In Apache 2.4 (bash-prompt.net)
Check the sample startup script to enable brotli apache module
After following the test instructions from the first link the line content-encoding: br from the output indicates that the server supports serving pages with brotli.
Hope this helps.