Hey @kenn - your timing is good! Back in Sep of 2022 another thread was started here on the forums about this exact same feature request.
Fast forward to today and we have a ticket actively looking at how we might add more Enketo widgets, specifically including the drawing widget which could be used for signatures.
I encourage you to review the forum thread and ticket to ensure you requirements will be met. Further, please add any other requirements or use cases of yours that might be missing from that thread.
Finally, if your use case is met by neither the thread or ticket, pleas let us know how it’s different and what you see might be some viable solutions might be.