I saw on a compatibility list that iWeb won't work on anything newer than Sierra. I haven't tested this yet, but I will. My website is built with iWeb, and until I get around to converting the site to something else, I'll still need to run iWeb. Since it's not something that I use very frequently, it's no problem running it from an external drive.
iWeb was dropped ten years ago and hasn't worked on any version of MacOS for a long Tim now. FWIW I switched to
Sparkle as the closest thing I could find to iWeb and it has only gotten better over the years since. At the time
Wordpress was also widely recommended as an option to iWeb.
BTW, the flickering problem didn't go away. One of the suggestions had been to uncheck the "Automatic graphics switching" option in the Energy Saver settings. Unfortunately, this option doesn't show up in my Energy Saver settings. The High Sierra version is the same as Sierra. So, they must have added that option in a later OS version. The flickering isn't excessive so far. I guess I'll have to live with it. And it seems to be okay with an external monitor. So I may use it that way until the computer dies completely. It's nearly six years old now. I don't think I can expect much more from it, considering how they build them these days. I guess it's time to start looking for a replacement.
If it is not showing up in the Energy Saver preference pane it could be because it is not supported by your specific hardware configuration. I have no idea when the "Automatic Graphics Switching" was added to MacOS, but if you search help on your Mac for
Automatic graphics switching it should show up in the help description if it is supported in your current version of Mac OS.
Your 15" Retina mid-2015 MBP has not yet reached
Vintage status, much less
Obsolete so it might be worth a trip to the Genius Desk at the nearest Apple Store to get them to run their diagnostic tests (they are not available to the public). If, as I suspect, the flicker is an indication of a failing graphics chip, display, or display connection that is the quickest and best way to identify the real problem, and will tell you if you need to start shopping seriously for a new MBP. Remember you will not be able to run the older versions of MacOS on any new Mac with Apple silicon inside so in any case you probably need to get serious about replacing iWeb in your workflow.
