On my Note9 the internet will work normally but when the device is left for a while the internet will stop working completely but will say it is still connected. Changing from wifi to cellular or cellular to wifi doesn't fix it, the only workaround I have found so far is to restart the phone.
This can happen multiple times a day and has been happening ever since the 'new' update last year.
Have reset network settings, reset access point names, factory restored the phone, and cleared cache partition. Yet the issue still occurs.