I think UNA CMS might not have built-in support for Brotli detection. However, you might be able to manually modify or adjust the configurations to use Brotli. Instead of relying on mod_deflate, you can modify the .htaccess file. I only use deflate_module

Something like this, but you should get confirmation from the UNA team or @LeonidS before trying it!

<IfModule mod_brotli.c>

  AddOutputFilterByType BROTLI_COMPRESS text/html text/plain text/xml text/css text/javascript application/javascript application/json

</IfModule>