Ok. Maybe removing only the 6 lines that add "!kerberos" as default here https://gitlab.com/Remmina/Remmina/-/blob/master/plugins/rdp/rdp_settings.c?ref_type=heads#L69 will be enough.
Leaving the new option "Auth settings FreeRDP auth-pkg-list" as is now, on the RDP global settings will be useful for users that still need to change auth-pkg-list from Remmina.

I'm happy to have been of help, it made me feel less old than I am ;).
You are doing a very good job with Remmina.

I will "use" the full patch daily when available on master (or better in the PPA, or even better in Ubuntu 24.04 if and when they will accept it).

I did some changes (on my Remmina fork, branch REM-3104) to move initialization of rdp_auth_filter setting at remmina startup.
In this way, the "!kerberos" option is immediately visible on the global RDP settings.
It seems to be working. To test it, you have to delete rdp_auth_filter from the ~/.config/remmina/remmina.pref file.
Here: https://gitlab.com/giox069/remmina-gio-fork/-/commit/e208cff836c75215c4bd9b04af4370b0856defe0

1st connection ok. Then I opened the setting window, an empty "rdp_auth_filter" has been saved into remmina.pref and subsequent connection failed. Maybe they failed because auth_list was empty string and not NULL. Quick and dirty workaround could be if (auth_list == NULL || rdp_auth_filter[0] == 0).

But I don't like it too much, because this option is not clearly exposed to the user in the settings... I'm looking for new ideas. Tomorrow.

I suggest a global RDP option, not a per profile one, to quicky solve this problem. Or users have to modify every single profile.

Maybe in the future a per profile option will be a better choice.

And Kerberos could be by default off: it has never been used before.

See issue #3104 (closed)

No patches for now from xfreerdp devel... maybe disabling kerberos from the remmina side like /auth-pkg-list:\\!kerberos and pushing that patch to Ubuntu 24.04 will be a good idea ? There is another issues due to Kerberos enabled by default in latest FreeRDP, making remmina not working: https://github.com/FreeRDP/FreeRDP/issues/10138

The PPA is working, but I have another problem: all RDP profiles using a numeric IP address instead of an hostname to connect to AD member PCs or Servers are failing with the following error:

Password:        
[15:12:12:874] [53053:0000cf3d] [ERROR][com.winpr.sspi.Kerberos] - [kerberos_InitializeSecurityContextA]: krb5_get_credentials (Configuration file does not specify default realm [-1765328160])
[15:12:12:874] [53053:0000cf3d] [WARN][com.winpr.sspi] - [winpr_InitializeSecurityContextA]: InitializeSecurityContextA status SEC_E_INTERNAL_ERROR [0x80090304]
[15:12:12:874] [53053:0000cf3d] [ERROR][com.freerdp.core.auth] - [credssp_auth_authenticate]: InitializeSecurityContext failed with SEC_E_INTERNAL_ERROR [0x80090304]
[15:12:12:874] [53053:0000cf3d] [ERROR][com.freerdp.core.rdp] - [rdp_recv_callback_int][0x633daabc4720]: CONNECTION_STATE_NLA - nla_recv_pdu() fail

xfreerdp3 has the same problem, and the current FreeRDP master branch too. I'm already writing to the FreeRDP devel for this. In the meanwhile the only workaround I have found for xfreerdp3 is to use /auth-pkg-list:\!kerberos in the xfreerdp3 command line.