Philip If you are still looking for suggestions, please see below.
All the documentation I can find registers the certificate in the device certificate store. Is there a sample where I can present a certificate directly to the SDK in code, or is there another way to do it?
Did you check the documentation on connecting to an IoT Edge device in the following article: Connect a downstream device to an Azure IoT Edge gateway?
The Azure IoT Edge SDK provides an option to register a CA certificate when setting up the client.
This operation doesn't install the certificate anywhere, but rather uses a string format of the certificate in memory. The saved certificate is provided to the underlying TLS stack when establishing a connection. Please see Use certificates with Azure IoT SDKs
The documentation also provides steps for different languages on how to use certificates with Azure IoT SDKs.
Hope this helps.
If you need further help in this matter, please comment in the below section and we are happy to discuss!
If this answers your query, do click Accept Answer and Yes for this answer as helpful. And, if you have any further query do let us know by commenting in the below section.