I've not yet tested it on a wide range of applications, however it's very easy to toggle back to the previous setting, so it seems low risk.
Google should find the iOS equivalent.
Note: This has nothing to do with problems accessing this board yesterday, as I discovered this after those problems.
Open the Settings app. 
Go to Connection & Sharing. 
Enter More Connection Settings. 
Tap on Private DNS. 
Select Private DNS provider hostname. 
Enter the following DNS address:dns.adguard-dns.com
Save the settings and exit. I discovered this after a friend bought a Xiaomi phone and initially that had problems with adverts everywhere including where you don't normally see them. With the help of google, we made a number of settings changes to fix that.
I tried this one on my Pixel.