Sony probably need to promote their new streaming client PS Portal and telling people they can use their old devices as well isn’t a good way to do so. But noone will say that officially I guess :)

Sadly there’s no (official) way for PS5 remote play on PS VITA.

I’m charging my phone every night due to Sleep as Android, so battery drain isn’t really a thing I’m looking after. But you are absolutely right here.

As already suggested you might take a look at IFTT.

Isn’t that the default behaviour? I never switch manually, but always use WiFi at home and mobile data when I’m out.

WiFi and mobile data are activated all the time.

Samsung Galaxy S10 Android 12