Connected to hotspot using create_ap but no internet connection. Please help

Question

Background info

This is a strange project. It's an on-going ubuntu experiment and learning experience for me.

I want to create a portable Plex Media Server on an External SSD ubuntu.

Firstly - I must emphasise that my ubuntu / linux knowledge is very novice. I am just try to self learn. I have zero background in IT or networking. My background is in Finance, so very little IT knowledge.

Why?

1. I want to have a Plex Media Server without depending on Internet access with me when I travel. I don't want to stream over the network from my home Plex Server. Don't want to incur network charges; also on some occasions I find internet access either bad or non existent. Hence, the portable Plex Media Server.
2. Why ubuntu? I am a ubuntu amateur, and I just want to further my knowledge on ubuntu to practical uses. I can use Windows (which I use at work) or MacOS (for personal home use), but I want a reason to use & learn ubuntu - hence, using it for the Plex Media Server as a start.
3. Why an external SSD bootable with ubuntu? Well, my travelling laptop will likely be a Windows machine (as I carry work with me). And when I want to switch off work, I want to boot into ubuntu.

What I am trying to achieve

My use case: is to have this portable Plex Media Server (on ubuntu) booted from external (2TB) SSD on my laptop (currently a Surface Pro 4), and to watch videos on the hotel room TV using a Google TV or Roku device connected to the TV via HDMI. For ease of this post, I will call the Plex Media Server on Ubuntu, booted from the external SSD as THE SERVER.

So what I need is to configure the  to connect THE SERVER to the internet using the hotel WiFi, and at the same time provide an access point so that the Google TV device connects to THE SERVER in order to watch the plex videos.

I have already created a bootable ubuntu on external SSD. I have tested the surface pro 4 booting from the external SSD. And I can setup the Plex Server no problems.

The problem I need help with

I am only unsure how to set up the WiFi AND create the access point at the same time.

I've searched the net for guides on how to do this, and the one that seems closest are the following: How to use wifi & enable hotspot at the same time https://linuxh2o.com/how-to-use-wifi-enable-hotspot-at-the-same-time/

I also followed the question and responses on How do I create a WiFi hotspot sharing wireless internet connection (single adapter)? and used the oblique's create_ap solution by https://askubuntu.com/users/402335/kcdtv

(I didn't try the other solution by https://askubuntu.com/users/147044/radu-r%c4%83deanu because I'm an ubuntu newbie and editing config files and making shell scripts scares me because I don't understand most of it. I try not to do things I don't fully understand.)

So, I've managed to install hostapd and used the create_ap to create the access point from THE SERVER, however while the Google TV device can see the access point SSID, it cannot connect. So I am not sure what is the problem.

Appreciate if you can guide me on resolving this? Also, in the event I'm done with the access point - how do I disable it.

See some technical details below. Let me know if there any other details I need to check and provide.

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Technical details:

• Using sudo lshw -class network - The wireless card on my Surface Pro 4 is made by Marvell Semiconductor, product 88W8897 [AVASTAR] 802.11ac Wireless.
• Using iw list - the network card supports AP interface modes. And the valid interface combinations include #channels <= 1.
• given I am using the same hardware as AP and also the WiFi connection, I used the command - sudo create_ap wlan0 wlan0 hotspotSSID hotspotpassword
• I used the wlan0 connection name as per ifconfig
• I note that dnsmasq had issues: failed to create listing socket for port 53: Address already in use