In OpenLMIS, we added a 'Contact Support' link right in the main menu to make it easy for end-users to share any kind of feedback or get help.
When users click 'Contact Support', they get a few choices of what type of support: technical support, reporting an issue, suggesting an improvement. Each of those has an easy form with just two or so fields to fill out. For bugs, it prompts the user for details and allows a screenshot.
Below is an animated GIF that shows this sequence.
We used Atlassian's JIRA Service Desk to gather and track all submissions. That tool does require internet connectivity, so for ODK a different tool to collect the feedback probably makes sense. But at least this UI might be helpful as you consider this.