[OnePlus 3 & 3T Cross Device Development] :
Great report! Just one ugly drawback: Adding linebreaks may look like a good idea because of the long lines, but putting a linebreak between the date and pid information and the info part of the same original line makes it a pain in the arse to grep through it:

--------- beginning of system
[ 01-14 00:12:23.080 461: 469 I/QISL ]
QSEE Interrupt Service Listener Thread is started

[ 01-14 00:12:23.081 461: 469 I/QISL ]
QSEE Interrupt Service Listener was activated successfully

For future reüorts don't add these linebreaks, please.

For your issue:

Somethings wrong with your webview setup:

ingo@adler /usr/local/src/los16 $ grep libwebview /mnt/export/data/Downloads/incoming/fc_logcat_1.txt
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Failed to load library libwebviewchromium.so: dlopen failed: library "libwebviewchromium.so" not found
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Failed to load library libwebviewchromium.so: dlopen failed: library "libwebviewchromium.so" not found
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Failed to load library libwebviewchromium.so: dlopen failed: library "libwebviewchromium.so" not found
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Failed to load library libwebviewchromium.so: dlopen failed: library "libwebviewchromium.so" not found
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
Caused by: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/system/app/webview/webview.apk"],nativeLibraryDirectories=[/system/app/webview/lib/arm64, /system/app/webview/webview.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]] couldn't find "libwebviewchromium.so"
ingo@adler /usr/local/src/los16 $

Somehow you've managed to mess up your webview setup. Did you disable/freeze/uninstall/remove webview? Did you install a third party webview?

ingo@adler /usr/local/src/los16 $ grep -B1 "Loading com.android.webview version" /mnt/export/data/Downloads/incoming/fc_logcat_1.txt
[ 01-09 22:22:17.378 7903: 7903 I/WebViewFactory ]
Loading com.android.webview version 79.0.3945.111 (code 1578013930)
--
[ 01-09 22:22:17.758 7903: 7903 I/WebViewFactory ]
Loading com.android.webview version 79.0.3945.111 (code 1578013930)
--
[ 01-09 22:22:27.987 9178: 9178 I/WebViewFactory ]
Loading com.android.webview version 79.0.3945.111 (code 1578013930)
--
[ 01-09 22:22:28.303 9178: 9178 I/WebViewFactory ]
Loading com.android.webview version 79.0.3945.111 (code 1578013930)

79.0.3945.111 is NOT the version nlos shipps with.

Replacing system files is no good idea - and this system modification is missing in your setup description.

If you are unhappy with tne shipped version (what's the problem, why do you felt the need to replace it?), you can always install com.google.android.webview from playstore and select it in dev-opts. Now you can easily switch between these on the fly (no reboot needed - just restart the webview using app).