comments:
It may be possible to clone the extra settings into a replacement router to duplicate the functionality of the ISP router. I don't really have any more detail to offer on that personally, just that it's not inherently 100% impossible. Most mesh systems will allow you to run them in Access Point mode. The existing router keeps working exactly as it is, and the mesh APs just broadcast the Wi-Fi signal. If you can, it's probably best to disable the ISP router's Wi-Fi in this case, so that all of the Wi-Fi stuff can be handled by the interconnected mesh system. With any mesh system, it's best if you can wire them into the network. Then they're essentially just wired-to-wireless converters and you can place them anywhere Wi-Fi coverage is needed. If the nodes are connecting back to your network via Wi-Fi, that means you need to place them in range of the main router's Wi-Fi, and you've now got two wireless hops in every connection (twice as much chance for interference, signal obstruction, etc.). The Deco BE25 3-pack is currently on sale for $200. https://www.amazon.com/dp/B0DKVDZXSN/ It's got a pretty stripped-down UI, requires a phone app to configure and manage, and is only dual-band. But if you're not concerned about 6GHz and don't need to do much more than reserve IPs and set a DNS server, it seems to be a decent PnP mesh system. It's working well so far for my parents (using wired backhaul).
Buy something like this: https://a.co/d/0gQ4TjI0 When you connect these, you have a main "hub" that creates the network when plugged into your Internet provider's router. Ideally you want the hub close to a line of sight between the other mesh node you're installing in your office/shed. Then you can put the third mesh node close to where you have the majority of your usage, like near the TV or another computer. This is likely the least expensive, easiest solution you have here and definitely don't need to hire anyone to do this for you. Feel free to ask any questions I can help with.
🔥 covers up to 6,600 sq. ft. = strong signal in more rooms https://amzn.to/43osiuc