I found a massive difference in connection to my cameras by changing from 1.1.1.1 to 4.4.4.4 on my DNS settings.
It used to take ages for my iPhone to connect until I changed the DNS servers. No other changes. Just that and now my cameras connect almost instantly.
Background. I’ve been in some sort of IT as a paid career for at least 28 years including working as a network engineer for an ISP so I know my stuff.