How to debug coredump in lz4 file format in manjaro with lldb?

I'm developing an application with C++14/clang/cmake/lldb toolchain in Manjaro Linux. And it produces some coredumps while testing. For example:

$ ls -la /var/lib/systemd/coredump/
core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000.lz4

How could I debug this ? I tried with 2 options:

1. decompress lz4 file and use lldb -c.
2. use coredumpctl debug.

For option-1:

$ sudo unlz4 core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000.lz4

It gives me: core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000.

Then lldb -c core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000.

Then bt all, which gives me:

(lldb) target create --core "core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000"
error: Unable to find process plug-in for core file '/var/lib/systemd/coredump/core.myapp-test.1000.1faf20db6d6048a18c4b6d28ea2776ee.1973.1590231863000000000000'
(lldb) bt all
error: invalid process

Option-1 failed.

For option-2:

$ coredumpctl list

It gives me:

TIME                            PID   UID   GID SIG COREFILE  EXE
Sat 2020-05-23 19:04:24 CST    1973  1000  1000   6 present   /home/linrongbin/workspace/myapp/debug/test/myapp-test

Then: $coredumpctl debug 1973

It gives me:

...
Failed to invoke gdb: No such file or directory

Option-2 failed as well.

So, for option-1, how could I decompressed lz4 coredump successfully and debug it? For option-2, how could I invoke lldb in coredumpctl ?