You should be able to use an external barcode scanner with Survey13. Just make sure 1) you can connect the barcode scanner to your device (most can connect via Bluetooth) and 2) you can configure the barcode scanner to behave like a keyboard against your host device. If these two conditions are met, open your Survey123 form and move to a question of type text. While the cursor is active in your text question, trigger the barcode scanner. The barcode content will pop in your text question.
I found a bluetooth scanner to borrow and it pairs as a watch with my Samsung Tab S3 android tablet and as far as I can tell there is no way to switch the type of device you are pairing via bluetooth. Anyway around this? The scanner scans my blood tubes perfectly where as the camera through Survey123 does not.