Set WorkerUpdate.channel to pypi if Spyder is not installed by conda.

Fixes spyder-ide#22572

spyder/plugins/updatemanager/widgets/update.py

@@ -612,7 +612,7 @@ def manual_update_messagebox(parent, latest_release, channel):
             ).format(dont_mix_pip_conda_video)
         else:
             if channel == 'pkgs/main':
-                channel = ''
+                channel = '-c defaults'
             else:
                 channel = f'-c {channel}'
 

spyder/plugins/updatemanager/workers.py

@@ -172,6 +172,7 @@ def __init__(self, stable_only):
         self.releases = None
         self.update_available = False
         self.error = None
+        self.channel = None
 
     def _check_update_available(self):
         """Checks if there is an update available from releases."""
@@ -200,12 +201,15 @@ def start(self):
         error_msg = None
         url = 'https://api.github.com/repos/spyder-ide/spyder/releases'
 
-        # If Spyder is installed from defaults channel (pkgs/main), then use
-        # that channel to get updates. The defaults channel can be far behind
-        # our latest release
-        if is_anaconda():
-            channel, channel_url = get_spyder_conda_channel()
-            if channel == "pkgs/main":
+        if not is_conda_based_app():
+            self.channel = "pypi"  # Default channel if not conda
+            if is_anaconda():
+                self.channel, channel_url = get_spyder_conda_channel()
+
+            # If Spyder is installed from defaults channel (pkgs/main), then
+            # use that channel to get updates. The defaults channel can be far
+            # behind our latest release.
+            if self.channel == "pkgs/main":
                 url = channel_url + '/channeldata.json'
 
         headers = {}