On Android Secure Web with MAM SDK, accessing internal websites shows error 'ERR_EMPTY_RESPONSE'. 
Further checking the logs, we see that Secure Web does not tunnel the connection to AG for internal websites. But for Legacy SDK, it works fine. 
Split Tunne - ON
DNS suffixes - ADDED

In the logs, we see clearly that connections are not tunnelled: 

"2020-10-20T17:50:16.797+0530","MVPN-MITM-ProxyTask","DEBUG5 (10)","Remote Host:internal.website.com RemotePort: 443",16849,18107,Secure Web,  ,  ,0
"2020-10-20T17:50:16.798+0530","MVPN-MITM-SplitTunnel","DEBUG5 (10)","Using split tunnel mode - ON. Should tunnel internal.website.com results to false.",16849,18107,Secure Web,  ,  ,0
"2020-10-20T17:50:16.798+0530","MVPN-MITM-ConnectFactory","DEBUG5 (10)","******* Establishing a new connection to internal.website.com:443 mode:direct",16849,18107,Secure Web,  ,  ,0
"2020-10-20T17:50:16.802+0530","MVPN-MITM-HttpsServer","ERROR ( 2)","Exception while connecting to remote: Unable to resolve host "internal.website.com": No address associated with hostname
java.net.UnknownHostException: Unable to resolve host "internal.website.com": No address associated with hostname

In the Legacy MDX logs, we see successful access for same website:

"2020-09-31T10:55:53.398+0400","MDX-MITM-ProxyTask","DEBUG5 (10)","Remote Host:internal.website.com RemotePort: 443",4490,4740,Secure Web,  ,  ,0
"2020-09-31T10:55:53.399+0400","MDX-MITM-SplitTunnel","DEBUG5 (10)","Using split tunnel mode - ON. Should tunnel internal.website.com results to true.",4490,4740,Secure Web,  ,  ,0
"2020-09-31T10:55:53.399+0400","MDX-MITM-ConnectFactory","DEBUG5 (10)","******* Establishing a new connection to internal.website.com:443 mode:AG",4490,4740,Secure Web,  ,  ,0
"2020-09-31T10:55:55.567+0400","MDX-MITM-HttpsServer","DEBUG5 (10)","Started proxy for connection to internal.website.com:443",4490,4756,Secure Web,  ,  ,0
"2020-09-31T10:55:55.572+0400","MDX-MITM-AGRequest","INFO ( 4)","fqdn formed : https://internal.website.com",4490,4756,Secure Web,  ,  ,0
"2020-09-31T10:55:55.572+0400","MDX-MITM-AGRequest","INFO ( 4)"," url to be accessed : /SecureBrowse/https/internal.website.com/",4490,4756,Secure Web, 

With MAM SDK, we should add internal website URL's under Intranet Applications for XenMobile Gateway in addition to DNS suffix entries. 
Refer below screen shots for adding it on XenMobile Gateway: 

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Problem Cause

In MAM SDK, Secure Web relies follows Netscaler’s Intranet Application entries in order to make tunneling decisions, as suggested in NetScaler’s documentation.