Why would you use a nest unit. That is a another expensive box that is packaged in a "decorator" case. You should not use mesh stuff unless you have no other option. A much cheaper standard router tends to be a better choice when you only need a single unit.
Never heard of the "onhub" but this should be a example we show all the people chanting....cloud,cloud,cloud. When the vendor of a device only supports admin via the network or some special app you run the risk of what happens if they go out of business or just decide to not support it any more.
If I had a dishonest company I would sell devices and as soon as the sales started to slow I would close that company and repackage the product as something new.
Many years ago when cisco owned linksys they tried this and got massive hate from the review sites and quickly added in a web browser local configuration. It seems we have a huge number of consumers who are just dumb and think cool things like using voice commands to their electronics is more important that long term functionality.
In this case you are pretty much out of luck. A quick search shows it uses a qualcomm cpu which means you have zero hope of third party firmware. Qualcomm does not want to provide information at all to the third party firmware community.