Update .github/workflows/linux.yml

Author: greg7mdp

.github/workflows/linux.yml

@@ -10,10 +10,10 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-22.04]
-        compiler: [g++-9, g++-10, clang++-17]
+        os: [ubuntu-latest]
+        compiler: [g++-, clang++]
+        flags: [-std=c++20]
         optimize: [-O2]
-        standard: [20]
 
     env:
       CXX: ${{ matrix.compiler }}