Are you seeing lots of traffic attributed to the (Other) or Unassigned channel in the traffic acquisition reports in Google Analytics?
A channel group is a collection of traffic source categories on your website that are grouped based on predefined rules. By default, Google Analytics provides a set of predefined channels for the Default Channel Group.
The (Other) grouping is for traffic sources that Google does not recognise as standard.
In Universal Analytics, it was possible to customize the default channel group to align with your UTM structure. However, in GA4, you will need to either:
Custom channel groups can be used in any report that already supports default channel group as a primary dimension (such as the Acquisition reports). You can use custom channel groups as a secondary dimension.
In your Google Analytics account go to Reports > User acquisition and change the primary dimension to be Source / Medium. Then add a filter for Default Channel Group to exactly match (Other).
On the left, click Admin
In the Property column, click Data Settings > Channel Groups
The table lists the default channel group and any additional groups you've created
From this location, you can:
To create a channel group, you can duplicate an existing group and make adjustments to it. In case you haven't created any groups before, you can begin with a replica of the default group. Alternatively, if you have previously created other groups, you can use one of those as a template or duplicate the default group.
Traffic is included in the first channel whose definition it matches given the current order of channels in the group.
Open Channel Groups
Click Create new channel group to start with a copy of the default group
OR
In the row for an existing group, click More > Copy to create new
Click Add new channel or click More > Copy to create new.
Name the channel or change the name of the copied channel
New Channel: Click Add condition group. Select the dimensions and dimension values to define the channel.
Copied Channel: Modify the existing condition and optionally add new conditions to define your new channel
In the row for an existing group, click >.
In summary, custom channel groups in GA4 allow you to tailor your traffic analysis to align with your marketing goals and gain deeper insights into your marketing channels' performance. This will help you make data-driven decisions to optimize your marketing efforts.