If you insert your sim card into another phone do you get similar pop up messages and if you can insert another sim card in your current phone.
There are some previous threads here >
https://eu.community.samsung.com/t5/galaxy-a-series/offline. , https://eu.community.samsung.com/t5/galaxy-s9-series/offline-internet and https://www.technipages.com/fix-google-for-android-shows-as-offline
Some information within these may help and there are other hits via a Google search.
Just to add you can reset network settings via Settings > General Management > Reset > Reset Network Connections.
I understand all is working OK but this action may help to stop these intrusive pop up warnings.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I have no affiliation with Samsung.