docs(flatpak): add common problems fix to troubleshooting.md (#1811)

docs/troubleshooting.md

@@ -5,6 +5,7 @@
 - [Linux](#linux)
   - [Fonts showing up as rectangles](#linux-fonts-rectangle)
   - [Global menu workaround for KDE](#linux-kde-global-menu)
+  - [Flatpak most common issues](#linux-flatpak-most-common-issues)
 - [macOS](#macos)
   - [App can't be opened because Apple cannot check it for malicious software](#macos-unidentified-developer)
   - ["VSCodium.app" is damaged and can’t be opened. You should move it to the Bin](#macos-quarantine)
@@ -34,6 +35,26 @@ On Ubuntu this package is called `libdbusmenu-glib4`.
 
 Credits: [Gerson](https://gitlab.com/paulcarroty/vscodium-deb-rpm-repo/-/issues/91)
 
+#### <a id="linux-flatpak-most-common-issues"></a>*Flatpak most common issues*
+
+- blurry screen with HiDPI on wayland run:
+  ```bash
+  flatpak override --user --nosocket=wayland com.vscodium.codium
+  ```
+- To execute commands on the host system, run inside the sandbox
+  ```bash
+  flatpak-spawn --host <COMMAND>
+  # or
+  host-spawn <COMMAND>
+  ```
+- Where is my X extension? AKA modify product.json
+  TL;DR: use https://open-vsx.org/extension/zokugun/vsix-manager
+
+- SDKs
+  see [this](https://github.com/flathub/com.vscodium.codium?tab=readme-ov-file#sdks)
+
+- If you have any other problems with the flatpak package try to look on the [FAQ](https://github.com/flathub/com.vscodium.codium?tab=readme-ov-file#faq) maybe the solution is already there or open an [issue](https://github.com/flathub/com.vscodium.codium/issues).
+
 ## <a id="macos"></a>macOS
 
 Since the App is signed with a self-signed certificate, on the first launch, you might see the following messages: