On Apache, we need to prevent double-compression by mod_brotli (in addition to mod_deflate). See https://httpd.apache.org/docs/2.4/mod/mod_brotli.html
If mod_brotli is enabled and active for text/css and text/javascript, a Drupal site's precompressed CSS and JS cannot be loaded by the browser (Failed to load resource: net::ERR_CONTENT_DECODING_FAILED) so I'm classifying this as a bug rather than feature request.