[OnePlus 5T  ROMs, Kernels, Recoveries, & Other Dev] skroute:
Albright i've found how to get logs and another captive portal WiFi.

Logcat.txt (with Android webview)

03-01 01:44:32.290 I/ActivityManager(1300): START u0 {act=android.net.conn.CAPTIVE_PORTAL flg=0x10400000 cmp=com.android.captiveportallogin/.CaptivePortalLoginActivity (has extras)} from uid 1000
03-01 01:44:32.327 I/ActivityManager(1300): Start proc 20120:com.android.captiveportallogin/u0a39 for activity com.android.captiveportallogin/.CaptivePortalLoginActivity
03-01 01:44:32.429 D/CaptivePortalLoginActivity(20120): onCreate for http://www.google.com/gen_204
03-01 01:44:32.553 E/AndroidRuntime(20120): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.captiveportallogin/com.android.captiveportallogin.CaptivePortalLoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.replaceAll(java.lang.String, java.lang.String)' on a null object reference
03-01 01:44:32.553 E/AndroidRuntime(20120):	at com.android.captiveportallogin.CaptivePortalLoginActivity.getHeaderTitle(CaptivePortalLoginActivity.java:527)
03-01 01:44:32.553 E/AndroidRuntime(20120):	at com.android.captiveportallogin.CaptivePortalLoginActivity.onCreate(CaptivePortalLoginActivity.java:141)
03-01 01:44:32.554 W/ActivityManager(1300): Force finishing activity com.android.captiveportallogin/.CaptivePortalLoginActivity
03-01 01:44:33.056 W/ActivityManager(1300): Activity pause timeout for ActivityRecord{6b5523c u0 com.android.captiveportallogin/.CaptivePortalLoginActivity t2546 f}
03-01 01:44:33.298 I/WindowManager(1300): Failed to capture screenshot of Token{aa7bc5 ActivityRecord{6b5523c u0 com.android.captiveportallogin/.CaptivePortalLoginActivity t2546 f}} appWin=Window{e064ab1 u0 Splash Screen com.android.captiveportallogin EXITING} drawState=4
03-01 01:45:25.888 I/ActivityManager(1300): START u0 {act=android.net.conn.CAPTIVE_PORTAL flg=0x10400000 cmp=com.android.captiveportallogin/.CaptivePortalLoginActivity (has extras)} from uid 1000
03-01 01:45:25.926 I/ActivityManager(1300): Start proc 20509:com.android.captiveportallogin/u0a39 for activity com.android.captiveportallogin/.CaptivePortalLoginActivity
03-01 01:45:25.978 D/CaptivePortalLoginActivity(20509): onCreate for http://connectivitycheck.gstatic.com/generate_204
03-01 01:45:26.089 E/AndroidRuntime(20509): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.captiveportallogin/com.android.captiveportallogin.CaptivePortalLoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.replaceAll(java.lang.String, java.lang.String)' on a null object reference
03-01 01:45:26.089 E/AndroidRuntime(20509):	at com.android.captiveportallogin.CaptivePortalLoginActivity.getHeaderTitle(CaptivePortalLoginActivity.java:527)
03-01 01:45:26.089 E/AndroidRuntime(20509):	at com.android.captiveportallogin.CaptivePortalLoginActivity.onCreate(CaptivePortalLoginActivity.java:141)
03-01 01:45:26.091 W/ActivityManager(1300): Force finishing activity com.android.captiveportallogin/.CaptivePortalLoginActivity
03-01 01:45:26.596 W/ActivityManager(1300): Activity pause timeout for ActivityRecord{d382d31 u0 com.android.captiveportallogin/.CaptivePortalLoginActivity t2549 f}

Device_info.txt

build.board: msm8998
build.bootloader: unknown
build.brand: OnePlus
build.cpu_abi: arm64-v8a
build.cpu_abi2:
build.device: OnePlus5T
build.display: omni_oneplus5t-userdebug 8.1.0 OPM1.171019.018 27 test-keys
build.fingerprint: OnePlus/OnePlus5T/OnePlus5T:8.0.0/OPR6.170623.013/12191451:user/release-keys
build.hardware: qcom
build.host: devbox2.omnirom.org
build.id: OPM1.171019.018
build.manufacturer: OnePlus
build.model: ONEPLUS A5010
build.product: OnePlus5T
build.radio: unknown
build.serial: 879ea7e3
build.tags: test-keys
build.time: 1519517278000
build.type: userdebug
build.user: jenkins
version.codename: REL
version.incremental: 27
version.release: 8.1.0
version.sdk_int: 27