This was happening to me also and it finally became so aggravating that I hunted down a solution. Here’s what I’ve done to fix it on a Mac.
You will need to have root privileges to do this. I did this in Terminal from the command-line as well, I’m not sure if you can edit system Library files from Finder with root privileges.
I located the DxO configuration file in the /Library/Preferences/DxO/Nik Collection directory - it’s called NikCollection.cfg. Full pathname /Library/Preferences/DxO/Nik Collection/NikCollection.cfg
Best to make a backup of this before changing it. I copied it off to another filename.
Edit the NikCollection.cfg file which is in XML format. Locate the entry “Checkforupdate” followed by a string with key name=“LastCheck” and a value=[some long number]. The long number is a date in Unix seconds-since-epoch; mine (1624306007) means DxO checked for update on Mon Jun 21 13:06:47 PDT 2021. Using your editor, change the long number to something much larger - I changed the leading 1 to be a 2 (“2624306007”, or Thu Feb 27 13:53:27 PST 2053). This means that Nik won’t check for an update again until sometime in 2053.
If you’re not used to command-line and root privileges, here’s a starting point. This isn’t meant to be a Unix tutorial and YMMV:
Open Terminal
From the command line, enter
sudo nano /Library/Preferences/DxO/Nik Collection/NikCollection.cfg
enter your password
You should have the file open, you can make changes to it, save it and exit.