I hope your key configuration on the servers allows to fix it 
It looks like you are using the very old URL of “discourse.destinationlinux.network” this is not the url. The correct URL is forum.tuxdigital.com and that is what the cert is valid for. The previous url that you show in the error was changed to the new one in 2020.
google.com is “very old” but “active and in use” is more important 