Update WebServer Config To Support Smush Pro

I'm running a WordPress site that was created using "WordPress on App Service". The Smush plugin (image optimisation) is included by default. I've purchased a Pro license for the plugin and would like to use the Local Webp feature. This requires the following to be added to nginx config:

# BEGIN SMUSH-WEBP
location ~* "wp-content\/(uploads\/)(.*\.(?:png|jpe?g))" {
	add_header Vary Accept;
	set $image_path $2;
	if (-f "/var/www/wordpress/wp-content/smush-webp/disable_smush_webp") {
		break;
	}
	if ($http_accept !~* "webp") {
		break;
	}
	expires	max;
	try_files /wp-content/smush-webp/$image_path.webp $uri =404;
}
# END SMUSH-WEBP

My question is how can I do this with the container used for this AppService? I've read other articles, e.g. https://techcommunity.microsoft.com/t5/apps-on-azure-blog/configure-nginx-for-php-8-linux-azure-app-service/ba-p/3069373, however the container is different.

I've created a file at /home/nginx.conf.default which contains the update (above). When I check the status of nginx (service nginx status) is reports stopped - even after a fresh start. Any attempt to start it shows the following error:

2023/11/22 11:39:08 [emerg] 7533#7533: bind() to 0.0.0.0:80 failed (98: Address in use)

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)

2023/11/22 11:39:08 [emerg] 7533#7533: bind() to 0.0.0.0:80 failed (98: Address in use)

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)

2023/11/22 11:39:08 [emerg] 7533#7533: bind() to 0.0.0.0:80 failed (98: Address in use)

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)

2023/11/22 11:39:08 [emerg] 7533#7533: bind() to 0.0.0.0:80 failed (98: Address in use)

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)

2023/11/22 11:39:08 [emerg] 7533#7533: bind() to 0.0.0.0:80 failed (98: Address in use)

nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)

2023/11/22 11:39:08 [emerg] 7533#7533: still could not bind()

I'm assuming another webserver is running? Is there a way to update the config of the webserver to include the smush config?