from the article:

For several years Sony had offered a free “External Monitor” app that let you use select Xperia-branded phones as an external display for some of the company’s high-end cameras. The Xperia 1 VII originally shipped without that feature, but now you can use the phone as camera display… if you pay at least $5 per month or $50 per year for a subscription.

Not only that, but for older phones that had these features for free, with the new version of the app, some features are locked behind subscription:

But on August 28, 2025, Sony announced an update that “expanded paid plan lineup for greater flexibility.” That flexibility locks a few key features behind a paywall, including:
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