diff --git a/docs/conf.py b/docs/conf.py
index 09e3823da..c0e36cfab 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -323,10 +323,10 @@ def configure_doxyfile(
 
 # Resolve GitHub link branches: env var → current docs branch → default.
 # Computed here so they are available both in the ReadTheDocs clone block and in extlinks.
-fastdds_fallback_branch = resolve_fallback_branch("FASTDDS_BRANCH", docs_branch, "master")
-fastdds_docs_fallback_branch = resolve_fallback_branch("FASTDDS_DOCS_BRANCH", docs_branch, "master")
-fastdds_python_fallback_branch = resolve_fallback_branch("FASTDDS_PYTHON_BRANCH", docs_branch, "master")
-fastdds_gen_fallback_branch = resolve_fallback_branch("FASTDDS_GEN_BRANCH", docs_branch, "master")
+fastdds_fallback_branch = resolve_fallback_branch("FASTDDS_BRANCH", docs_branch, "3.4.x")
+fastdds_docs_fallback_branch = resolve_fallback_branch("FASTDDS_DOCS_BRANCH", docs_branch, "3.4.x")
+fastdds_python_fallback_branch = resolve_fallback_branch("FASTDDS_PYTHON_BRANCH", docs_branch, "2.4.x")
+fastdds_gen_fallback_branch = resolve_fallback_branch("FASTDDS_GEN_BRANCH", docs_branch, "4.2.x")
 
 print("Fallback branches for GitHub links:")
 print('  Fast-DDS:        "{}"'.format(fastdds_fallback_branch))
@@ -376,7 +376,7 @@ def configure_doxyfile(
                 fastdds_branch
             )
         )
-        fastdds_branch = "origin/master"
+        fastdds_branch = "origin/3.4.x"
 
     # Actual checkout
     print('Checking out Fast DDS branch "{}"'.format(fastdds_branch))
@@ -399,7 +399,7 @@ def configure_doxyfile(
                 fastdds_python_branch
             )
         )
-        fastdds_python_branch = "origin/main"
+        fastdds_python_branch = "origin/2.4.x"
 
     # Actual checkout
     print('Checking out Fast DDS Python branch "{}"'.format(fastdds_python_branch))
diff --git a/readthedocs.yaml b/readthedocs.yaml
index 016d04b47..bdba5d0b2 100644
--- a/readthedocs.yaml
+++ b/readthedocs.yaml
@@ -6,7 +6,7 @@
 version: 2
 
 build:
-  os: ubuntu-20.04
+  os: ubuntu-22.04
   tools:
     python: "3.11"
   apt_packages: