I thought it would be possible to connect the phone (s22 u) to a private wifi network without internet and be able to use / share the internet of the phone, or even search the internet (via the mobile) while still connected to the wifi without internet.
Is there a setting to allow this? I thought that the option to use the mobile internet if the wifi internet weakened or dropped off would do it, but it doesn't. Any help would be appreciated.
Just needs a little lateral thinking. Using a modem/router you can set up a network which doesn't have internet access on a particular network. Sadly my DSL netork quite often connects the network but says 'no internet. It is easy to do intenally just know your modem/router settings. Given most routers support both 2.4G and 5G networks it is easy to isolate one network but usually this will be the 2.4G network as many devices don't yet work on 5G. You may, I emphase may, be able to set up a guest network on the router which allows this so you keep both existing networks internet connected. When you want to update just change the settings.whilst updating. Alternatively use an old modem/router lying around to create another network. Bit messier for updating. A nice bit of extra protection if you want an internal network that can't be hacked because of no internet. In passing, I have a dual sim phone and I can turn off data download for either or both phone numbers. However you might have to get another printer unless your current printer allows both wireless and hard-wired (usb) printer connection at the same time (it should do, showing as two different printer options).
