Sure, you would test-install apps via any delivery method of your choice, including USB-C cable or WiFi, after Google attests that your test-app signature is whitelised[0]. After all, there is no legitimate reason[1] to not sign your app, since you want it to closely match the distributed version as much as possible, and there won't exist unsigned distributable apps.

0. Developer has valid signatures and in Google's good graces, and application hasn't been installed on more than 16 devices

1. Oh, you CI/CD signing infra won't let you? You better fix your workflows to match the Google way.