The practice itself is malignant, either explicitly ask upon first run or require a MEILI_YES_ANALYTICS env variable to enable it.
This is already pretty invasive - it discloses activity, number of machines deployed, IP address which identifies location and often organizations and individuals (and which is considered protected personal data per the GDPR afaik).
> The privacy of the users is kept.
No it isn't, see above - even as the authors you don't get to decide what data does or doesn't infringe upon the users privacy.
> It just serves us to know if our work is being used.
This is irrelevant, if you want to condition the use of your work on being let known where and how it is being used then license it accordingly and abide by the applicable laws.