Comment # 6 on bug 1085616 from V��t��zslav ������ek

(In reply to Antonio Crevill��n from comment #3)
> Can the user enable insecure encryption?

Yes, and Leap-15/Factory still does support some of the old ciphers.

To see the list of all the supported ciphers run
# ssh -Q cipher
3des-cbc
aes128-cbc
aes192-cbc
aes256-cbc
rijndael-cbc@lysator.liu.se
aes128-ctr
aes192-ctr
aes256-ctr
aes128-gcm@openssh.com
aes256-gcm@openssh.com
chacha20-poly1305@openssh.com

Here you can see that some of the ciphers offered by your Oracle Linux are
supported (aes256-cbc, aes192-cbc, aes128-cbc, 3des-cbc).
They just aren't part of the default setup (see man ssh_config).

The solution for you will be passing the cipher spec parameters to ssh:
# ssh -c "aes256-cbc,aes192-cbc,aes128-cbc,3des-cbc" -l user 192.168.1.12

You can also add this host-specific setup to your ssh_config.