I can find no way to turn of merge of main into pull request before running actions

[esbennielsenkvantify]

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GitHub always merge our main branch into the pull request branches before running CI actions. Are there anyway of stopping that behaviour?

My problems are:

1. The code running on CI is not identical to the code I have checked out on my machine, that makes it much harder to debug issues.
2. I want the ability to work my own issues before I rebase or merge with main first, catching my breath not worrying about other peoples changes just yet.
3. I want CI actions to run even though I have merge conflicts with main - again I do not want to be forced to fix those up front.
   (Discussed in https://github.com/orgs/community/discussions/26304)

I can partly understand why this was done to try in a cheap fashion to run CI on code very similar to code ending up on main after merge, but to me it looks like an experimental feature, which I at least should be able to switch off. I have tried BitBucket/Bamboo, Jenkins and GitLab. None of them does this.