Logitech k480. I carry it everywhere. Has a three way switch, iPhone, iPad and Mac. Only problem is it interferes with headphones/wifi somehow. Mac cries piteously when the k480 connects.

On “field trips” where laptop is too much and just the iphone is too little, I have been pairing my ipad with a k380 for the last 200 years and cannot complain much. The only warning I get is that k380 causes some kind of interference with the apple pencil and other bluetooth connected devices. Can’t precise exactly how much though.

I've always wanted a phone keyboard that folds yet still types reasonably well. Tried a few, hated them all.