worked out some bugs

jupyter_lab_config.py

@@ -1,9 +1,76 @@
 import logging
 import platform
 
+from io import StringIO
 from itertools import product
 from os import environ
 from pathlib import Path
+from subprocess import CalledProcessError, run
+
+logging.getLogger(__name__).propagate=True
+
+def find_flatpak_browser():
+    if platform.system() != "Linux":
+        return
+    
+    for path_element in map(Path, environ["PATH"].split(":")):
+        if (path_element/"flatpak").is_file():
+            flatpak_bin = path_element/"flatpak"
+            break
+    else:
+        # flatpak is not installed
+        return
+    
+    flatpak_apps = ("com.google.Chrome", "com.microsoft.Edge", "com.brave.Browser", "org.chromium.Chromium")
+
+    try:
+        flatpak_process = run(
+            [
+                str(flatpak_bin),
+                "list",
+                "--app",
+                "--columns=application"
+            ],
+            capture_output=True,
+            check=True
+        )
+    except CalledProcessError as e:
+        pass
+    else:
+        with StringIO(flatpak_process.stdout.decode()) as flatpak_output:
+            installed_flatpaks = flatpak_output.readlines()[1:]
+        
+        for flatpak_app in flatpak_apps:
+            if flatpak_app in [_.strip() for _ in installed_flatpaks]:
+                return f"flatpak run --filesystem={Path.home()/'.local/share/jupyter/runtime'} {flatpak_app} --start-maximized --profile-directory=Default --app=%s"
+
+
+def find_browser():
+    # find a chromium-based browser on the system to use. 
+    if platform.system() == "Windows":
+        # prefers Microsoft Edge on Windows
+        cmds = (
+            "Microsoft/Edge/Application/msedge.exe",
+            "Google/Chrome/Application/chrome.exe",
+        )
+        path_elements = map(Path, (environ["ProgramFiles"], environ["ProgramFiles(x86)"]))
+
+    elif platform.system() == "Linux":
+        # prefers Google Chrome on Linux due to popularity of the browser
+        cmds = ("google-chrome", "microsoft-edge", "brave", "chromium")
+        path_elements = map(Path, environ["PATH"].split(":"))
+
+    elif platform.system() == "Darwin":
+        # also prefers Google Chrome on MacOS due to popularity of the browser
+        cmds = ("Contents/MacOS/Google Chrome", "Contents/MacOS/Microsoft Edge")
+        path_elements = [Path(f"/Applications/{Path(cmd).name}.app") for cmd in cmds]
+
+    # use the first chromium-based browser found as the browser to run Jupyter in app mode
+    for cmd, path_element in product(cmds, path_elements):
+        browser = path_element / cmd
+        if browser.exists():
+             return f'"{browser}" --start-maximized --profile-directory=Default --app=%s'
+
 
 # generated if you run `jupyter lab --generate-config`, used for additional configuration
 DEFAULT_CONFIG_FILE = Path.home() / ".jupyter/jupyter_lab_config.py"
@@ -11,33 +78,10 @@ DEFAULT_CONFIG_FILE = Path.home() / ".jupyter/jupyter_lab_config.py"
 # user's home will be the root path of jupyter's file explorer
 c.ServerApp.root_dir = str(Path.home())
 
-# find a chromium-based browser on the system to use. 
-if platform.system() == "Windows":
-    # prefers Microsoft Edge on Windows
-    cmds = (
-        "Microsoft/Edge/Application/msedge.exe",
-        "Google/Chrome/Application/chrome.exe",
-    )
-    path_elements = map(Path, (environ["ProgramFiles"], environ["ProgramFiles(x86)"]))
+browser_cmd = find_flatpak_browser() or find_browser()
 
-elif platform.system() == "Linux":
-    # prefers Google Chrome on Linux due to popularity of the browser
-    cmds = ("google-chrome", "microsoft-edge", "brave", "chromium")
-    path_elements = map(Path, environ["PATH"].split(":"))
-
-elif platform.system() == "Darwin":
-    # also prefers Google Chrome on MacOS due to popularity of the browser
-    cmds = ("Contents/MacOS/Google Chrome", "Contents/MacOS/Microsoft Edge")
-    path_elements = [Path(f"/Applications/{Path(cmd).name}.app") for cmd in cmds]
-
-# use the first chromium-based browser found as the browser to run Jupyter in app mode
-for cmd, path_element in product(cmds, path_elements):
-    browser = path_element / cmd
-    if browser.exists():
-        c.ServerApp.browser = (
-            f'"{browser}" --start-maximized --profile-directory=Default --app=%s'
-        )
-        break
+if browser_cmd:
+    c.ServerApp.browser = browser_cmd
 else:
     logging.getLogger(__name__).warning(
         "No Chromium-based browser was found on this system, therefore Jupyter will run "