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Developer mode

With dumbsms installed on your Mac, the next step is getting the phone ready. Before dumbsms can read or send texts, the phone has to expose the Android debug bridge (ADB). That means turning on Developer options and USB debugging. Both phones here are real AOSP Android — not KaiOS — but they unlock developer mode differently.

Sonim XP3plus

XP3900 · standard Android unlock

The Sonim uses the normal Android recipe. If you've ever enabled developer mode on a Pixel or Samsung, this will feel familiar. It's also the faster dumbsms phone — about 10× the TCL over Bluetooth (~15 K/s vs ~1.2 K/s).

Unlock path Settings → About Phone → Build number
  1. Open Settings → About Phone.
  2. Highlight Build number and press the center OK button (or tap) 7 times. Watch for the countdown toast → "You are now a developer!" (you may be asked for your lock PIN).
  3. Back out to Settings. Developer options now appears (usually near About Phone or under System).
  4. Open Developer options → USB debugging → ON.
  5. Plug into your computer. Run adb devices or open dumbsms and accept the Allow USB debugging? prompt on the phone.

TCL Flip Go

4058W · Android 11 · hidden unlock

The TCL Flip Go is genuine AOSP Android 11, but TCL renamed and hid the usual Build number field. KaiOS tricks (secret dialer codes, WebActivity hacks, Konami soft-key sequences) do not apply — this phone is not KaiOS.

Expect a slow data link — roughly 10× slower than the Sonim, especially over Bluetooth (~1.2 K/s vs ~15 K/s). Texts are fine; first syncs and MMS photo pulls just take longer.

Unlock path Settings → About Phone → Software information → SVN
  1. Open Settings → About Phone → Software information.
  2. You'll see Software version and SVN (each opens a version dialog). Highlight SVN.
  3. Press the top SoftLeft soft key (the physical button directly under the left side of the screen — not the D-pad left, not the center OK button) about 7–8 times. Watch the bottom of the screen for the countdown → "You are now a developer!"
  4. Back out to Settings. Developer options appears at the bottom of About Phone / under Phone Settings.
  5. Open Developer options → USB debugging → ON.
  6. Plug into your computer and accept the authorization prompt. The device should list as device, not unauthorized.

What did not work on the TCL

  • Secret dialer codes (*#*#33284#*#*, etc.) — those are for KaiOS phones, not this one.
  • Tapping "Build number". There is no Build number field on this firmware; the equivalent target is SVN.
  • KaiOS WebActivity / Engmode routes. No Settings → Device menu exists on this Android build.

After USB debugging is on

Both phones follow the same path from here:

  1. Connect with a data-capable USB cable. Accept the RSA fingerprint prompt on the phone.
  2. On the computer, make sure no stray adb server is blocking direct access — dumbsms talks to the phone without the adb binary. If something else already claimed the device, run adb kill-server or use the stop adb server button in Settings.
  3. Open dumbsms to confirm the connection. The status bar at the bottom left should show connected.
  4. On the TCL Flip Go, install the companion app from Settings — retail firmware only allows one sideloaded package (see The one app this phone will install).