Using ssh keys for subversion authentication on RHEL 6, 7 & 8

We are currently just starting using RHEL 8 and I've been tasked with migrating our Subversion server from RHEL 6 to RHEL 8

I have found that the existing dsa ssh keys we used on RHEL 6 are not supported on RHEL 8
So I created an rsa ssh key on a RHEL8 dev box for connecting to a RHEL 8 Subversion Server as per the RHEL 8 documentation
This works fine from RHEL 8 to RHEL 8, but when I try and use the rsa key generated above on a RHEL 6 box, it doesn't work.
When I try and ssh-add the key on RHEL 6, it doesn't accept the passphrase that works on RHEL8

Is there a suggested way that ssh keys should be generated and used across the RHEL platforms ?

Alec Keeler, Build & Release Engineer