Same issue on higher version - not solved - so no support for Oracle DB on Ubuntu:
pm@pm-VirtualBox:~$ ldd /opt/oracle/instantclient_21_17/libsqora.so.21.1
linux-vdso.so.1 (0x00007e1564695000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007e1564679000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007e1564590000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007e156458b000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007e1564586000)
libaio.so.1 => not found
libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007e1564571000)
libclntsh.so.21.1 => /opt/oracle/instantclient_21_17/libclntsh.so.21.1 (0x00007e155fc00000)
libclntshcore.so.21.1 => /opt/oracle/instantclient_21_17/libclntshcore.so.21.1 (0x00007e155f600000)
libodbcinst.so.2 => /lib/x86_64-linux-gnu/libodbcinst.so.2 (0x00007e156455d000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007e155f200000)
/lib64/ld-linux-x86-64.so.2 (0x00007e1564697000)
libnnz21.so => /opt/oracle/instantclient_21_17/libnnz21.so (0x00007e155ea00000)
libaio.so.1 => not found
libaio.so.1 => not found
libltdl.so.7 => /lib/x86_64-linux-gnu/libltdl.so.7 (0x00007e1564550000)