How to configure Apache in order to proxy Plex (by Adrian P.)

Home

Step 1:

Replace anywith
RewriteCond %{HTTP_HOST} 		^(.*):(.*)$

RewriteCond %{HTTP_HOST} 		^(.*):(.*)$
RewriteCond %{QUERY_STRING} 		!X-Plex
RewriteCond %{HTTP:X-Plex-Product} 	!\w+

Step 2:

Replace anywith
RewriteCond %{HTTP_HOST} 		!^(.*):(.*)$

RewriteCond %{HTTP_HOST} 		!^(.*):(.*)$
RewriteCond %{QUERY_STRING} 		!X-Plex
RewriteCond %{HTTP:X-Plex-Product} 	!\w+

Step 3 (http with no security and port restrictions -> valid for non-Zyxel users too):

This configuration won't work if the Plex's port specified with "Server is mapped to port" (by default is 32400) is not accessible!
Replace (if you have it) AuthZyxelSkipPattern with AuthZyxelSkipPattern /plex, .
Include the code below outside of any </VirtualHost> directive. 
# BEGIN plex
RewriteRule ^/plex/?$	/plex/web/index.html	[R=301]
<location /plex/>
	ProxyPass			http://127.0.0.1:32400/
	ProxyPassReverse		http://127.0.0.1:32400/
	ProxyPassReverseCookiePath 	/		/plex/
	ProxyPassReverseCookieDomain	127.0.0.1	adrhc.asuscomm.com
</location>
# END plex
Put the code above between <VirtualHost *:443> and </VirtualHost> in order to access plex over https too but with same restrictions related to ports.

Step 3 (http with no security and NO port restrictions -> valid for non-Zyxel users too):

Replace (if you have it) AuthZyxelSkipPattern with AuthZyxelSkipPattern /plex, .
Include the code below outside of any </VirtualHost> directive. 
# BEGIN plex
RewriteRule 					^/plex/?$ 		/web/index.html 		[R=301]

ProxyPass					/web/			http://127.0.0.1:32400/web/
ProxyPassReverse				/web/			http://127.0.0.1:32400/web/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPass					/photo/:/		http://127.0.0.1:32400/photo/:/
ProxyPassReverse				/photo/:/		http://127.0.0.1:32400/photo/:/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPass					/:/websockets/		http://127.0.0.1:32400/:/websockets/
ProxyPassReverse				/:/websockets/		http://127.0.0.1:32400/:/websockets/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPassMatch 					^/(\w+-\w+-\w+-\w+-\w+)$	http://127.0.0.1:32400/$1
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

RewriteCond 					%{REQUEST_URI} 			!^/plexx
RewriteCond 					%{HTTP:X-Plex-Product} 		\w+
RewriteRule 					.*	 			http://%{HTTP_HOST}/plexx%{REQUEST_URI}?%{QUERY_STRING} [NE,B]

RewriteCond 					%{REQUEST_URI} 	!^/plexx
RewriteCond 					%{QUERY_STRING} X-Plex
RewriteCond					%{REQUEST_URI}	!^/photo/:/
RewriteRule 					.*		http://%{HTTP_HOST}/plexx%{REQUEST_URI}?%{QUERY_STRING} [NE,B]

ProxyPass			/plexx/	http://127.0.0.1:32400/
ProxyPassReverse		/		http://127.0.0.1:32400/
ProxyPassReverseCookiePath	/		/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name
# END plex

Step 3 (with https and requiring Zyxel console authentication):

Replace AuthZyxelSkipPattern with AuthZyxelSkipPattern /plex, .
Include the code below EXACTLY before </VirtualHost> which is enclosing <VirtualHost *:443> directive. 
# BEGIN plex
RewriteRule 					^/plex/?$ 		/web/index.html 		[R=301]

ProxyPass					/web/			http://127.0.0.1:32400/web/
ProxyPassReverse				/web/			http://127.0.0.1:32400/web/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPass					/photo/:/		http://127.0.0.1:32400/photo/:/
ProxyPassReverse				/photo/:/		http://127.0.0.1:32400/photo/:/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPass					/:/websockets/		http://127.0.0.1:32400/:/websockets/
ProxyPassReverse				/:/websockets/		http://127.0.0.1:32400/:/websockets/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

ProxyPassMatch 					^/(\w+-\w+-\w+-\w+-\w+)$	http://127.0.0.1:32400/$1
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name

RewriteCond 					%{REQUEST_URI} 			!^/plexx
RewriteCond 					%{HTTP:X-Plex-Product} 		\w+
RewriteRule 					.*	 			https://%{HTTP_HOST}/plexx%{REQUEST_URI}?%{QUERY_STRING} [NE,B]

RewriteCond 					%{REQUEST_URI} 	!^/plexx
RewriteCond 					%{QUERY_STRING} X-Plex
RewriteCond					%{REQUEST_URI}	!^/photo/:/
RewriteRule 					.*		https://%{HTTP_HOST}/plexx%{REQUEST_URI}?%{QUERY_STRING} [NE,B]

ProxyPass			/plexx/	http://127.0.0.1:32400/
ProxyPassReverse		/		http://127.0.0.1:32400/
ProxyPassReverseCookiePath	/		/
ProxyPassReverseCookieDomain	127.0.0.1	replace_this_with_your_wan-ip_or_domain-name
# END plex
Step 4 (valid for both http with no security and port restrictions and http with no security and NO port restrictions):

Access this url in order to open Plex page:
https://replace_this_with_your_wan-ip_or_domain-name/plex

Step 4 (with https and requiring Zyxel console authentication):

First: login using the Zyxel administration console; the url it's something like the one below (the exact one depends on your installed firmware version):
https://replace_this_with_your_wan-ip_or_domain-name/r39679,/adv,/loginwrap.html
Second: in order to access Plex page open a new browser tab with the following url:
https://replace_this_with_your_wan-ip_or_domain-name/plex
* It's important to use only https; won't work over http.