There are tester machines available via aliexpress. I didn’t include a link because their links are insanely long but do a search for “iphone 6s screen tester” on their main page and you will see some machines.
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IMHO, having a spare housing that is known-good is great for troubleshooting purposes. You can accumulate some iCloud locked devices and give them a useful life.
I haven’t used these machines so take this for what it’s worth.
There are tester machines available via aliexpress. I didn’t include a link because their links are insanely long but do a search for “iphone 6s screen tester” on their main page and you will see some machines.
I haven’t used these machines so take this for what it’s worth.