@Bert-1n, With a crack in the back you can be sure it is NOT waterproof. In my experience the NORMAL phones that pretend to be waterproof actually are NOT to the level that can be used on a bike in heavy rain. RUGGED phones are a different story. We have been plowing through rain for two days last week. My CAT said it detected water in the headphone jack and asked if it should be disabled. Things like that you won't find in an ordinary phone. In case of heavy rain I pull out the USB port and close the lid of the charger. My phone almost runs a whole day on battery in the brightest setting, so that is no problem. Also most rugged phones can be used with ordinary gloves. Normal phones can't. Nice extra is that many rugged phones are pretty cheap and a lot cheaper than a Zumo XT. Besides that it handles spotify or any music service you can think of, does the Flitsmeister app, and you have only one device to pair with your headset.
There are really not many aspects of a dedicated navigation device that are not handled better by a rugged phone. However I would welcome an Android based device with an integrated charging mount like the Zumo's and TT's
Since I use my CAT phone dedicated on my bike, I had no problem using this cheap solution for a mount:
https://www.emounting.nl/lampa-titan-opti-ball-head-25-mm.html
With a this sticker on the back of the phone:
https://www.emounting.nl/opti-universal-connector-voor-opti-line-bevestigin.html