It seems since samba 4.16 libunwind is a dependency but not required by default.
After upgrading from 4.15.5-1 to 4.16.0-4 I noticed the following error:
$this->bbcode_second_pass_quote('', 'A')pr 02 20:45:19 raspberry nmbd[392]: /usr/bin/nmbd: error while loading shared libraries: libunwind-aarch64.so.8: cannot open shared object file: No such file or directory
Apr 02 20:45:19 raspberry smbd[393]: /usr/bin/smbd: error while loading shared libraries: libunwind-aarch64.so.8: cannot open shared object file: No such file or directory