Custom ROMs replace Samsung's One UI with a clean, bloat-free Android experience. LineageOS offers pure AOSP with extensive customization, while Pixel Experience delivers Google's Pixel UI with all Pixel-exclusive features. This guide walks you through installing a custom ROM on your Galaxy S26 Ultra.

Prerequisites

Before starting, you need: a rooted Galaxy S26 Ultra with unlocked bootloader, TWRP recovery installed (see our TWRP guide), the custom ROM ZIP file downloaded for your exact model (SM-S938B), a GApps package (if the ROM does not include Google apps), and a full Nandroid backup created in TWRP.

Warnings: Custom ROMs may break Samsung-specific features like Samsung Camera processing, S-Pen pressure sensitivity in certain apps, and Samsung Health sensors. Knox features are already gone if you are rooted. Some ROMs may not support all hardware features on Day 1 — check the ROM's thread on XDA for known bugs.

Step 1: Download the ROM and GApps

Visit XDA Developers and find the ROM thread for the Galaxy S26 Ultra (search for your model number). Download the latest stable build ZIP file. For LineageOS, download GApps separately (MindTheGapps or NikGapps recommended for Android 16). Pixel Experience includes Google apps by default — no separate GApps needed.

Transfer both ZIP files to your phone's internal storage or a USB OTG drive.

Step 2: Create a Full Backup in TWRP

This is critical — if the custom ROM does not work properly, you can restore your backup to return to your previous state.

  1. Boot into TWRP recovery (Power + Volume Up while powered off).
  2. Tap Backup.
  3. Select: Boot, System, Data, Vendor, EFS, Modem.
  4. Swipe to start backup. Wait for completion.
  5. Copy the backup folder to your PC for safe storage.

Step 3: Wipe the Device

In TWRP:

  1. Tap Wipe.
  2. Tap Advanced Wipe.
  3. Select: Dalvik/ART Cache, System, Data, Cache, Vendor.
  4. Do NOT wipe Internal Storage (your ROM ZIP is there) or EFS.
  5. Swipe to wipe.
Never wipe the EFS partition unless you have a verified backup. EFS contains your IMEI — wiping it bricks your cellular connectivity.

Step 4: Flash the Custom ROM

  1. In TWRP, tap Install.
  2. Navigate to the ROM ZIP file on internal storage.
  3. Select it and swipe to flash.
  4. Wait for the flash to complete (2-5 minutes).
  5. If using LineageOS or another ROM without built-in GApps, tap Install again and flash the GApps ZIP immediately — do NOT reboot between ROM and GApps.
  6. Optionally flash Magisk ZIP to maintain root access on the new ROM.

Step 5: First Boot

Tap Reboot → System in TWRP. The first boot takes 5-15 minutes as the new ROM initializes. Do not force reboot during this time.

Once the setup wizard appears, configure your device: language, Wi-Fi, Google account, and permissions. You are now running a custom ROM on your Galaxy S26 Ultra.

LineageOS vs Pixel Experience — Quick Comparison

LineageOS: Pure AOSP base, extensive customization options in Settings, no Google apps by default (add what you want), lighter on resources, longer battery life, active development community with weekly builds, Privacy Guard built in.

Pixel Experience: Looks and feels exactly like a Google Pixel, all Pixel features included (Now Playing, Call Screening, Pixel Launcher, Google Assistant integration), Google apps pre-installed, monthly security updates following Pixel schedule, Google Camera with full processing pipeline.

How to Switch Back to One UI

If you want to return to Samsung's One UI:

  1. Boot into TWRP and restore your Nandroid backup, OR
  2. Download stock Samsung firmware and flash via Odin (see our Flash Tool guide).

Troubleshooting

Bootloop after flashing ROM: Boot into TWRP, do a full wipe (Dalvik, System, Data, Cache, Vendor), and reflash the ROM. If it still bootloops, the ROM may not be compatible with your variant — check the XDA thread for your model.

No cellular service: Flash the correct modem/baseband for your model. Download stock firmware, extract the CP_*.tar.md5, and flash only the modem via TWRP or Odin.

Google Play not working: You either did not flash GApps or flashed an incompatible GApps version. Reflash ROM + correct GApps version (match Android version).

Camera quality is poor: Custom ROMs do not include Samsung's proprietary camera processing. Install Google Camera (GCam) mod for significantly better photo quality on custom ROMs.

S-Pen not working: Some custom ROMs have incomplete S-Pen support. Check the ROM's known issues list before flashing.

Guide by XDA Unlocker Team. Last updated: July 2026.

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Written by

XDA Unlocker Team

GSM Repair Technician & Firmware Specialist

Professional GSM technician with 15+ years of experience in Samsung firmware, FRP bypass, ISP pinout and hardware-level diagnostics. We provide verified, step-by-step repair guides for technicians worldwide.

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