diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index b4bc431..526ee8e 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -10,17 +10,17 @@ name: R-CMD-check
 
 jobs:
   R-CMD-check:
-    runs-on: ${{ matrix.config.os }}
+    runs-on:  ubuntu-latest
 
-    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
+    name: (${{ matrix.config.r }})
 
     strategy:
       fail-fast: false
       matrix:
         config:
-          - {os: macos-latest,   r: 'release'}
-          - {os: windows-latest, r: 'release'}
-          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {r: 'devel'}
+          # minimal required R version
+          - {r: '3.6.0'}
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
       R_KEEP_PKG_SOURCE: yes
@@ -33,7 +33,6 @@ jobs:
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
-          http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
 
       - uses: r-lib/actions/setup-r-dependencies@v2