Hi @kuba ,
ho, thats not a simple question . I will share my thoughts gladly, but I certainly know only superficially about the technical depths of this problem. Maybe we can start a broader discussion with other community members here, that would be great. Let me comment about the different directions as you pointed them out:
- Using Piwik Pro as a GTM server side template: this would be quite a convenient solution for many people who want to hold GTM as their favorite tool. Nonetheless I think this could run into problems as Firefox and Safari are already blocking gtm.js from scratch in their policies (e.g. see the findings of Markus Baersch concerning this subject https://www.campixx.de/media/ServersideGTM_MarkusBaersch.pdf).
- Dedicated PP solution: As far as I understand the browsers ITP/ETP approach , all solutions using central and recognizable (external) endpoints (as somepoint.piwik.pro) may experience the same problems as GTM and may be blocked in the near future. If that would be the case, only server side solution on premise or at least on the same TLD could be used as a reliable endpoint…
But maybe I do not realise other possibilities… (?)