I just type away in Notes and Mail on iOS and trust that the text processing / data detectors will automagically convert / link / mark down the URL when you press Done in notes or save the draft in Mail.
I've never needed to use Command K on iOS for any of the apps. Other apps of course have more enhanced processing of links. Pages for one immediately converts a link and has link settings when you tap once and release on the link.
Outlook as well has a tap and hold insert menu that lets you add a link in an analogous way to some OS on the Command + K
One slick way to get fancy styled notes is to open notes and then open Pages as a multitasking pop up to make the adjustments. In the second image I replaced the text for Apple's web site with the text WOOOO and then copied / pasted that into Notes.
Notes can handle the full equivalent of markdown [WOOOO](https://www.apple.com) and render it properly. It just lacks the UI controls to generate such links with a presentation different than the simple data detector label with the link.