In GA4 reports, the use of regex features such as the negative lookahead syntax (e.g., ?!) is not supported. An attempt to use such syntax, like ^(?!.*consent-mode).*ga4.*$, will result in an error message stating Unsupported regular expression syntax in value.

To filter reports in GA4 using regex, you can utilize the Explore section which allows for filtering with Full Regex. Instead of trying to do everything in one complex regex pattern, you can simply enter the pattern to include and then the pattern to exclude separately within the report functionality to achieve the desired result.

The simpler alternative to using complex regex in GA4 is to use the Explore section's report functionality. Here, you can separately enter the patterns to include and exclude, which avoids the need for complex regex syntax that might not be supported by GA4.