You might also find that any pre-existing saved signatures have similarly disappeared with the iPadOS 17 update - affecting both Notes drawing and system-wide markup tools. The markup magnifier tool is similarly absent from the latest release - despite still being documented within the updated iPad User Guide.
I note that elements are shared via iCloud sync' remain accessible to devices that have not yet been updated to iOS/iPadOS 17.
At present, the working hypothesis is a bug introduced with the latest release. Apple invite submission of Bug Reports via its Product Feedback portal. For iPad and iPadOS:
Feedback - iPad - Apple
If submitting a Bug Report, ensure that you include details of your iPad model and installed version of iPadOS within the body-text of your report. Don't rely upon the pick-list - as this rarely includes the current versions.
You might also be well advised to seek assistance directly from from Apple Support - as they may wish to record and escalate as appropriate. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044