it's impossible to verify as we don't know what data is actually being sent. But there's a hint in the ToS and that doesn't sound very anonymized.
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From their privacy policy: https://www.ui.com/legal/privacypolicy/#c1
The Usage Data that we collect may include information such as your device data, including your mobile devices, sensor data, device signals, device parameters, device identifiers that may uniquely identify your devices, including your mobile device, web request, Internet Protocol address, browser type, browser language, referring/exit pages and URLs, platform type, the date and time of your request, and one or more cookies that may uniquely identify your devices or browser. IN ADDITION, WE MAY AUTOMATICALLY COLLECT LOCATION INFORMATION (INCLUDING LATITUDE AND LONGITUDE), PERFORMANCE DATA, MOTION DATA, TEMPERATURE DATA, POWER USAGE DATA, AND ANY DATA OR SIGNALS COLLECTED BY THE DEVICES AS PART OF THE USAGE DATA. WE DO NOT COLLECT THE CONTENTS OF ANY COMMUNICATIONS THAT PASS THROUGH OUR DEVICES OR SERVICES.
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By this desription, it certainly isn't GDPR compliant. device identifiers/data etc.. is PII in GDPR context and requires a legal basis for processing.