Hi Stefan,
The thread that you've pointed to discusses a slightly different concern. Namely, tracking that can be implemented from within the extension. Mixpanel and Amplitude are indeed viable alternatives for that use case.
However, the question was about the use of GA-4 in the Chrome Web Store. Currently the Chrome Web Store only supports Google Analytics v3 which is set to EOL later this year. Most everyone has already moved their analytics from v3 to v4 (in anticipation of deprecation of v3), however Chrome Store still only supports v3 which makes it impossible for us to incorporate it into our analytics accounts.
Hope this makes sense.
Cheers,
Artem.