This is a great question, and you’ll find that your concerns are actually stated as requirements in industry standards concerning accessibility.
As you specifically mention gestures and long-press, I’ll answer to these first:
Gestures that require several fingers at once, or tracing a path on the screen (swiping, dragging) need to have an alternative, simple click/tap interaction.
Solutions I saw in the wild, that work well:
- an additional menu (three points, more, overflow menu)
- repeating the action on the detail page (like delete)
For long tap: Best practice might be to render the button additionally a toggle. I’ve seen this in several apps and it works well. I think Android’s camera uses this pattern.
Requirements on accessibility of software
I totally support Michael’s answer, in that the W3C guidelines usually can be applied to software in general, and the W3C guidelines on mobile accessibility are a great resource.
In Europe, we have our Accessibility requirements for ICT products and services, which refer to the WCAG, but also apply to software in general (chapter 11 Software).
For example:
All functionality that uses multipoint or path-based gestures for operation can be operated with a single pointer without a path-based gesture, unless a multipoint or path-based gesture is essential
11.2.5.1 Pointer gestures in EN 301 549