I found there're some problems related to secure file copy (scp) happened in Oracle 19c when OpenSSH is 8 or higher in Linux or AIX. More specifically, such errors are usually thrown during grid infrastructure (GI) installation and cluster verification utility (CVU) check.
First of all, check the release of OpenSSH. For example, in Linux
[root@primary01 ~]# ssh -V
OpenSSH_8.0p1, OpenSSL 1.1.1c FIPS 28 May 2019
Or in AIX.
[root@primary01 /]# ssh -V
OpenSSH_8.1p1, OpenSSL 1.0.2u 20 Dec 2019
As you can see, they are all OpenSSH 8 or higher version.
The workaround is to disable strict filename checking by adding an option -T to /usr/bin/scp command, according to scp manual page.
[root@primary01 ~]# cp -p /usr/bin/scp /usr/bin/scp-original
[root@primary01 ~]# echo "/usr/bin/scp-original -T \$*" > /usr/bin/scp
[root@primary01 ~]# cat /usr/bin/scp
/usr/bin/scp-original -T $*
Most checks related to copying file from the other nodes are gone.
For safety, you'd better keep the above setting unchanged even after you have installed grid infrastructure 19c and database binaries.