I have been "digiscoping" with smart phones for a long time, maybe since 2010 before many even heard of the term. Over the course of years i have used and tried many versions of what many call "smart phone adapters".
What is neat about smart phones is that the phone camera lens mimics almost exactly the human eye. So by placing your phone camera lens over an optical eyepiece and holding it "just so" you will be able to take a decent picture (image). The problem is "holding it just so", which smart phone adapters sold the problem... sort of.
Next problem, which optic and which smart phone will you use? Some smart phone adapters solve this problem by selling different adapters that fit a specific phone and a specific optic eyepiece size (usually given in mm's). The two parts usually "bayonet mount" together. So, if you are going to use only one optic (say a spotting scope and one brand/model of smart phone, you may elect this option. You will spend about $90 for both. These can be neat and handy, especially since you can use the smart phone adapter as a phone protective case (with the optic adapter removed).
The other option is a universal fits all "jig" apparatus with numerous adjustments to fit a particular optic/smart phone. These are obviously more expensive about $150. They work, but are cumbersome to use and set up. Bear in mind, I've used these in the past but no more.
Meopta's MeoPix UNI 2 in my opinion the best in the evolution of smart phone adapters. Easy to adapt to any smart phone (Android, Apple) and any size ocular lens. Set up is intuitive. And once set up, easy to take on an off your optic with a 1/4 turn of the ocular adapter ring. The MeoPix UNI 2 will set up back about $80 plus tax and shipping.
These are readily available now though your favorite retailer might have to wait a couple weeks for product to arrive from CZ.