You can add sigpatches to AIO updater as a custom download option.
I'm not sure I am permitted to post a link to a guide here, so here is a copy-pasted instructions:
- Extract aio-switch-updater.zip to your SD card.
- Enter All In One Switch Updater.
- Scroll down to Custom downloads and select the second Add a custom link button.
- Add the following to the Title and Linkfields:
- Title: Signature Patches
- URL: Insert a url for sigpatches (should end with ".zip")
Have fun)