Well Holy Crap @johnnyf1ve! I have been dealing with this same problem with Metronet for over 2 years. The cron script you initially wanted to implement is here. I've been using it for a long time to work around the issue.
I too have a Protectli appliance right after Metronet's Nokia modem. Bet you got one of those modem's too. I can say it's definitely not a hardware issue on my pfSense appliance because I've used the Protectli and tested with an old Dell with a Dual NIC Intel NIC. Same problems with dropped WAN.
I have long thought this is a unique problem with Metronet. They have cheap Fiber and you gotta cut costs somewhere. I have other Protectli boxes in other environments running with Metronet with the same result of losing the WAN connection. If you have a static IP from Metronet the problem of course goes away and that was the ultimate fix.
I just made the changes that you have found from the Reddit user and I'll see how it goes. I'll probably keep my Cron pintest.sh scheduled just in case. I can check the log files to see if it's actually resetting the interface after your suggestion. Thanks man!
Lastly, here are my last few pingtest.sh logs with the dropped connection from the past few weeks. When the ping test fails it turns the WAN interface off for a few seconds and then right back on which fixes the problem 99% of the time. As you can see, this happens a lot.
20220917.181601 All pings failed. Resetting interface igb0.
20220917.181635 All pings failed. Resetting interface igb0.
20220919.071749 All pings failed. Resetting interface igb0.
20220920.211301 All pings failed. Resetting interface igb0.
20220920.211335 All pings failed. Resetting interface igb0.
20220922.180104 All pings failed. Resetting interface igb0.
20220922.180138 All pings failed. Resetting interface igb0.
20220924.160249 All pings failed. Resetting interface igb0.
20220924.160323 All pings failed. Resetting interface igb0.
20220927.105456 All pings failed. Resetting interface igb0.
20220927.105530 All pings failed. Resetting interface igb0.
Thanks MEtroNeT!