You can easily bypass the mic pres on the iD24 by simply patching the output of your other mic preamps or gear into the insert return on input channels 1 or 2, which is a very pure differential line stage into the ADC, therefore completely bypassing the onboard mic pres and line input stage.
If you would like more information on setting up your iD24 with your outboard gear please read the article here;
https://audient.zendesk.com/knowledge/articles/12667748648468/en-us?brand_id=2283536