Basically the campaign capture in Matomo/Piwik (Pro) works similar to Webtrekk, but there are some differences that should be considered when changing providers.
Unlike the media code used in Webtrekk, Matomo (Piwik) uses pk parameters. In the free version two parameters are available (printed in bold), with the corresponding plugin another three, i.e. a total of five parameters plus ad media level (here called campaign ID, printed in grey). The parameters are:
pk_campaign (campaign name)
pk_medium (campaign medium) - newsletter, AdWords, display, social media etc.
pk_source (campaign source) - referrer
pk_keyword/kwd (campaign keyword) - for SEA
pk_content (campaign content) - for A/B variants
pk_cid (campaign ID)
It is completely optional which of these parameters should be recorded by Matomo (Piwik), but the recommendation is at least to record name, medium and source. This structure is very similar to the utm parameter of Google. For this reason, it is advisable to create at least five category levels plus advertising media levels in Webtrekk to ensure comparability.
The standard attribution model "last" can also be adapted to the model "first" in the tracking code. By default, the last referrer is displayed, direct calls are not taken into account. Alternative attributes (Last interaction, Last non direct interaction, First interaction, Linear, Position based, Time expiry) can be selected in the frontend.
Please note that a different attribution model may also result in other key figures for campaigns in Webtrekk.
For more information on the acquisition logic of Matomo/Piwik, see the following sources: