Your strace output shows that the comment fields ends with \r character, which is carriage return without newline, making the rest of the line overwriting the start of the line.

I do not see this byte in the file that I downloaded from the attachment to this bug (maybe it was converted during transfer in bugzilla?):

[jjelen@t490s crypto_policies (master)]$ hexdump -C ~/Downloads/id_rsa.test.pub | tail -2
00000190  37 41 0a                                          |7A.|

Can you run the above command yourself with the key you see this issue with?

The simple workaround is to use dos2unix utility before calling ssh-keygen.

I see last time it might have worked was the RHEL6 since the command did not list the comment at all (correct me if I am wrong, but I see there just a filename).

Reading through the code, there is really no handling of the windows end lines in the code as it prints whatever it reads from file. It looks like this is not handled inside of the getline() eitner, so it will probably require some more checks, but given the priority and simple workaround, I set the priority to low.

Created attachment 1733419 [details]
Proper id_rsa.pub created in Windows and shows ^M end line

Good day Jakub,

I uploaded the wrong key.  I apologize.  Take 2!

I'll upload the proper one this time, but with a hexdump we definitely see this:

$ hexdump -C id_rsa.pub | tail -n 2
00000190  37 41 0d 0a                                       |7A..|

And yes, the priority is low as we have multiple very easy work arounds to this issue.  Thank you for your help with this.

As for the comment:

    I see last time it might have worked was the RHEL6 since the command did not list the comment at all (correct me if I am wrong, but I see there just a filename).

That's the theory at this point.  The comment is causing us the grief.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: openssh security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:4368