Doesn't GDPR basically count as the perfect excuse as why they would count the same user installing as multiple installs?

Something along the lines of "we can't identify the device so we have to count it as a unique install"

> we can't identify the device

The post you're replying to seems to be more meaning "they shouldn't be receiving any information from (un)installers anyway".

So, them being able to count installs at all is the problem.

You can agree to telemetry under GDPR as a consumer.

GDPR relates to personal data and it doesn’t forbid sending any network packets to the USA.

In some contexts the IP address already counts as personal data. Wasn't there recently an issue with web sites using Google fonts and therefore transmitting the user's IP address to Google?

Multiple curts have ruled that the information "IP soandso visited page soandso" and "IP soandso downloaded font soandso" are personal data.

Therefore it is very likely they will rule the same for "IP soandso installed software soandso".

Are "corporate information", as PI for commercial entities, covered by GDPR?

They claim to have their own processes to count installs which would counter spoofing attacks. As well as being opaque to developers on how their installs are counted, this may be scooping up PII of users.

Unity already has UnityEngine.Analytics.dll since 2018, and it claims to be GDPR-compliant.

"Q: Is software made in unity going to be calling home to unity whenever it's ran, even for enterprice licenses? A: We use a composite model for counting runtime installs that collects data from numerous sources. The Unity Runtime Fee will use data in compliance with GDPR and CCPA. The data being requested is aggregated and is being used for billing purposes."

Source: https://forum.unity.com/threads/unity-plan-pricing-and-packa...

    use data in compliance with GDPR

That is what Google also claims.

But the curts have ruled such claims from US companies are worth nothing because the US government has access to that data and has not made such claims.

The cases you are referring to are Schrems I (which cancelled the Safe Harbor transfer agreement) and II (which cancelled the Privacy Shield). But, the commission ratified a new agreement between the EU and the USA in July, the DPF. So such transfers are now possible again, without any further protections. Until Schrems III, that is.

I'd like to know which legal basis is used for this processing.

Does it also mean that an internet connection is a requirement to play any Unity game? Including, for example, physical Switch cartridges?