framework: Better firmware update instructions and troubleshooting

framework/README.md

@@ -13,12 +13,38 @@ First put enable `fwupd`
 services.fwupd.enable = true;
 ```
 
+> [!Note]
+> For Intel CPU's, even [stable BIOS versions](https://community.frame.work/t/responded-11th-gen-intel-core-bios-3-17-release/25137#update-april-11-2023-2) are currently marked as [test versions](https://fwupd.org/lvfs/devices/work.frame.Laptop.TGL.BIOS.firmware) in LVFS (the default remote fwupd uses to get firmware).
+>
+> If you want to use these versions, you'll have to [explicitly enable the lvfs-testing remote](https://community.frame.work/t/responded-11th-gen-intel-core-bios-3-17-release/25137#linuxlvfs-7):
+>
+> ```nix
+> services.fwupd.extraRemotes = [ "lvfs-testing" ];
+> # Might be necessary once to make the update succeed
+> services.fwupd.uefiCapsuleSettings.DisableCapsuleUpdateOnDisk = true;
+> ```
+
+> [!Caution]
+> Before running the update, make sure you have a [NixOS live ISO](https://nixos.org/download/#nixos-iso) on a USB stick, because some firmware updates [make your system unbootable](https://community.frame.work/t/drive-not-bootable-after-bios-update/12887).
+
 Then run
 
 ```sh
  $ fwupdmgr update
 ```
 
+If you cannot boot into your system after upgrading:
+1. Boot into the live USB
+2. Mount your system into `/mnt`
+3. Run
+   ```
+   sudo nixos-enter
+   ```
+4. Run
+   ```
+   NIXOS_INSTALL_BOOTLOADER=1 /run/current-system/bin/switch-to-configuration boot
+   ```
+
 ## Common Modules
 
 For the Framework 13 laptops, there are common configuration modules available under the `13-inch/common/` directory,