diff --git a/lib/util/git/index.ts b/lib/util/git/index.ts
index 6df7303b275c57..763e6e1c87a580 100644
--- a/lib/util/git/index.ts
+++ b/lib/util/git/index.ts
@@ -768,6 +768,42 @@ export async function deleteBranch(branchName: string): Promise<void> {
   delete config.branchCommits[branchName];
 }
 
+export async function mergeBranchWithoutPushing(
+  branchName: string
+): Promise<void> {
+  let status: StatusResult | undefined;
+  try {
+    await syncGit();
+    await git.reset(ResetMode.HARD);
+    await gitRetry(() =>
+      git.checkout(['-B', branchName, 'origin/' + branchName])
+    );
+    await gitRetry(() =>
+      git.checkout([
+        '-B',
+        config.currentBranch,
+        'origin/' + config.currentBranch,
+      ])
+    );
+    status = await git.status();
+    await gitRetry(() => git.merge([branchName]));
+    incLimitedValue('Commits');
+  } catch (err) {
+    logger.debug(
+      {
+        baseBranch: config.currentBranch,
+        baseSha: config.currentBranchSha,
+        branchName,
+        branchSha: getBranchCommit(branchName),
+        status,
+        err,
+      },
+      'mergeBranch error'
+    );
+    throw err;
+  }
+}
+
 export async function mergeBranch(branchName: string): Promise<void> {
   let status: StatusResult | undefined;
   try {
diff --git a/lib/workers/repository/onboarding/branch/index.ts b/lib/workers/repository/onboarding/branch/index.ts
index 2add4def7375e7..8e7770bbe97e5b 100644
--- a/lib/workers/repository/onboarding/branch/index.ts
+++ b/lib/workers/repository/onboarding/branch/index.ts
@@ -8,7 +8,12 @@ import {
 } from '../../../../constants/error-messages';
 import { logger } from '../../../../logger';
 import { Pr, platform } from '../../../../modules/platform';
-import { checkoutBranch, setGitAuthor } from '../../../../util/git';
+import { scm } from '../../../../modules/platform/scm';
+import {
+  checkoutBranch,
+  mergeBranchWithoutPushing,
+  setGitAuthor,
+} from '../../../../util/git';
 import { extractAllDependencies } from '../../extract';
 import { mergeRenovateConfig } from '../../init/merge';
 import { OnboardingState } from '../common';
@@ -81,9 +86,16 @@ export async function checkOnboardingBranch(
     }
   }
   if (!GlobalConfig.get('dryRun')) {
-    logger.debug('Checkout onboarding branch.');
     // TODO #7154
-    await checkoutBranch(onboardingBranch!);
+    if (
+      await scm.isBranchConflicted(config.baseBranch!, config.onboardingBranch!)
+    ) {
+      logger.debug('Checkout onboarding branch');
+      await checkoutBranch(config.onboardingBranch!);
+    } else {
+      logger.debug('Merge onboarding branch in default branch');
+      await mergeBranchWithoutPushing(onboardingBranch!);
+    }
   }
   // TODO #7154
   const branchList = [onboardingBranch!];