There is no 64-bit libwidevine library, only 32-bit, which is why future LE 9.0 releases have switched to the same split 64-bit kernel, 32-bit userspace arrangement as Android. Please also note that Google's license for libwidevine means it is not redistributable without signing formal agreements that result large liabilities for the signing entity. Community or personal LE releases that ignore the license and embed libwidevine for convenience will be suspended from this forum if we become aware they are doing so, because we do not want the legal attention that may result from their release here. There is a Kodi helper add-on for inputstream.adaptive that provides the libwidevine library via a user-initiated process. If it hasn't appeared in the Kodi repo yet, it will do soon - it's inclusion was agreed by Kodi developers at the recent Prague DevCon.
I happen to have an ubuntu 'artful' chroot on my 'bleeding edge' gentoo kvim2 box and it seems chromium-browser ubuntu package does have a 64-bit libwidevine library couple:
(ubuntu) root@kvim2-gentoo:~# file /usr/lib/chromium-browser/libwidevinecdm.so
/usr/lib/chromium-browser/libwidevinecdm.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, BuildID[sha1]=7469dc485fb01b9a791a926eebc6be7e4c38b2a0, stripped
(ubuntu) root@kvim2-gentoo:~# file /usr/lib/chromium-browser/libwidevinecdmadapter.so
/usr/lib/chromium-browser/libwidevinecdmadapter.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, BuildID[sha1]=cddfee451f1ff47626705bdb016c1d668ae7771a, stripped
(ubuntu) root@kvim2-gentoo:~# lddtree /usr/lib/chromium-browser/libwidevinecdm.so
libwidevinecdm.so => /usr/lib/chromium-browser/libwidevinecdm.so (interpreter => none)
libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0
libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6
ld-linux-aarch64.so.1 => /lib/aarch64-linux-gnu/ld-linux-aarch64.so.1
libm.so.6 => /lib/aarch64-linux-gnu/libm.so.6
libgcc_s.so.1 => /lib/aarch64-linux-gnu/libgcc_s.so.1
libdl.so.2 => /lib/aarch64-linux-gnu/libdl.so.2
libglib-2.0.so.0 => /lib/aarch64-linux-gnu/libglib-2.0.so.0
libpcre.so.3 => /lib/aarch64-linux-gnu/libpcre.so.3
(ubuntu) root@kvim2-gentoo:~# lddtree /usr/lib/chromium-browser/libwidevinecdmadapter.so
libwidevinecdmadapter.so => /usr/lib/chromium-browser/libwidevinecdmadapter.so (interpreter => none)
libwidevinecdm.so => /usr/lib/chromium-browser/./libwidevinecdm.so
libm.so.6 => /lib/aarch64-linux-gnu/libm.so.6
libdl.so.2 => /lib/aarch64-linux-gnu/libdl.so.2
libglib-2.0.so.0 => /lib/aarch64-linux-gnu/libglib-2.0.so.0
libpcre.so.3 => /lib/aarch64-linux-gnu/libpcre.so.3
libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0
libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6
ld-linux-aarch64.so.1 => /lib/aarch64-linux-gnu/ld-linux-aarch64.so.1
libgcc_s.so.1 => /lib/aarch64-linux-gnu/libgcc_s.so.1
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So I will want to use these (in particular libpcre may be missing) in LE soon just for sake of trial.
Keep you informed!
update
The ubuntu 'artful' shared libraries when included load just fine.
But I see another, I guess addon specific, problem:
07:06:54.669 T:548472168464 ERROR: Previous line repeats 1 times.
07:06:54.669 T:548472168464 NOTICE: VideoPlayer::OpenFile: http://localhost:43898/manifest?id=80182440
07:06:54.670 T:548195717312 NOTICE: Creating InputStream
07:06:58.738 T:548195717312 ERROR: AddOnLog: InputStream Adaptive: License update not successful (no keys)
07:06:58.739 T:548195717312 ERROR: AddOnLog: InputStream Adaptive: Initialize failed (SingleSampleDecrypter)
07:06:58.741 T:548195717312 ERROR: CVideoPlayer::OpenInputStream - error opening [http://localhost:43898/manifest?id=80182440]
07:06:58.741 T:548195717312 NOTICE: CVideoPlayer::OnExit()
not a big issue for me as I hardly ever use Netflix (my wife does) but , at least, I have hope (for personal usage) it may eventually work in 64-bit LE ...
I can move discussion to Netflix addon thread perhaps.