You will need to install the Securly SSL certificate on your device to ensure that Securly is able to filter all HTTPS sites browsed there effectively. Note that the latest update to macOS Big Sur ...
I've just installed the included macOS 10.12 system certs from Leopard WebKit 604.5.6_2 dmg file on 10.4.11, but I can't really tell if it made a difference.
You will need to install the Securly SSL certificate on your device to ensure that Securly is able to filter all HTTPS sites browsed there effectively. Note that the latest update to macOS Big Sur ...