How to Flash a Custom ROM on Samsung Galaxy A21s (SM-A217F)

Preparing Your Samsung Galaxy A21s

• ⚠️ Back up all your data before starting, as the process will reset your phone.
• 📧 If your Google account is signed in, sign out of it from the phone's settings before proceeding.
• 📶 Connect your phone to a Wi-Fi network for the bootloader unlocking process.

Unlocking the Bootloader and Downloading Files

• 📱 Verify your phone's model number is SM-A217F to ensure compatibility with provided files; otherwise, you'll need to find specific files for your model.
• ⚙️ Enable Developer Options by tapping the build number seven times, then enable OEM unlocking within Developer Options.
• 🔌 Turn off the phone, then boot into Download Mode by holding Volume Up and Volume Down while plugging in the USB cable.
• 💻 Download essential files: Odin, Samsung drivers, TWRP custom recovery, vbmeta.tar, and the custom ROM (e.g., Evolution X).

Flashing TWRP Custom Recovery

• 🖱️ Install the Samsung USB drivers on your computer and restart your computer.
• 📂 Extract Odin and run the Odin executable.
• 🔌 Boot your phone into Download Mode again.
• 📲 In Odin, load the TWRP image into the AP slot and the vbmeta.tar file into the USERDATA slot.
• 🚫 Disable Auto Reboot in Odin's options.
• ▶️ Click Start to flash TWRP; if it fails, set up the phone briefly after unlocking the bootloader and try again.

Installing Custom ROM and GApps

• 🔄 After flashing TWRP, boot into recovery mode by holding Power and Volume Down, then switching to Volume Up when the screen goes black, and finally releasing Power when the Samsung logo appears.
• 🧹 In TWRP, perform a Format Data by typing 'yes', then go to Advanced Wipe and select Dalvik/ART Cache, Cache, System, and Data.
• 💾 Method 1 (Direct Install): Copy the custom ROM and GApps (e.g., NikGApps) zip files to your phone's internal storage and install them via TWRP's Install menu.
• 💻 Method 2 (ADB Sideload): If direct copy fails, install ADB on your computer, connect the phone in recovery mode, and use the adb sideload command in the terminal to flash the ROM and GApps zip files.
• 🚀 After flashing, reboot the system; the first boot may take a significant amount of time.

Post-Installation and First Boot

• ✨ The phone will boot into a new interface, resembling a Pixel experience, after the custom ROM is successfully installed.
• 🛠️ You can now set up your phone with the new custom ROM, including connecting to Wi-Fi and configuring settings.
• ↩️ If you wish to revert, a separate video guide for flashing the stock ROM is available.