Try a different env var reference syntax

appimage/AppImageBuilder.yml

@@ -31,7 +31,7 @@ AppDir:
     name: Twitch Drops Miner
     icon: io.github.devilxd.twitchdropsminer
     version: '{{APP_VERSION}}'
-    exec: usr/bin/python${{env.PYTHON_VERSION}}
+    exec: usr/bin/python{{env.PYTHON_VERSION}}
     exec_args: '${APPDIR}/usr/src/main.py $@'
 
   apt:
@@ -126,7 +126,7 @@ AppDir:
     env:
       PATH: '${APPDIR}/usr/bin:${PATH}'
       PYTHONHOME: '${APPDIR}/usr'
-      PYTHONPATH: '${APPDIR}/usr/lib/python${{env.PYTHON_VERSION}}/tkinter:${APPDIR}/usr/lib/python${{env.PYTHON_VERSION}}/site-packages'
+      PYTHONPATH: '${APPDIR}/usr/lib/python{{env.PYTHON_VERSION}}/tkinter:${APPDIR}/usr/lib/python{{env.PYTHON_VERSION}}/site-packages'
       APPDIR_LIBRARY_PATH: '${APPDIR}/usr/lib:${APPDIR}/usr/lib/x86_64-linux-gnu:${APPDIR}/lib/x86_64-linux-gnu'
       TCL_LIBRARY: '${APPDIR}/usr/share/tcltk/tcl8.6'
       TK_LIBRARY: '${APPDIR}/usr/lib/tcltk/x86_64-linux-gnu/tk8.6'