How to filter time-related images in Google Earth Engine and conduct regression analysis to verify the consistency of different sensors？

Landsat data harmony is shown on the Google developer website(https://developers.google.com/earth-engine/tutorials/community/landsat-etm-to-oli-harmonization), but I want to verify this harmony result by selecting sample points to merge. What should I do?
Below is a link to the original code(https://code.earthengine.google.com/798ae7a268f8e2c8022433b9562785c0)