Thanks
@ed.stein and Hi
@Stork, I think I understand,
even if you didn't answer me if it was only for the second monitor, but from the last sentence it seems clear to me that you said that the problem applies to everything.
Reading a bit on the Catalina forum, I happened to find that the problem with the DP occurred several times even with versions prior to 10.15.5, but I have never had problems with the RX580 (in orinoco as Stork indicated in the first installation guide and as suggested above), not even with the current card that worked a bit in orinoco at the beginning, then now it is without any particular setting. So due to the fact that it is a problem already present before, in some cases, I think it is not related to the specific of 10.15.5 and that if it worked in 10.15.4, it should also work in .5 and your solution should be in some settings. The problem is to put my hand on the fire
but as soon as I have some time I will try and at most return to .4 from the backup.
In any case I will update the info here ... and you too keep updating us, so we save each other's headaches.
Greetings and thanks