@fofkla ,
Thank you for the very helpful video.
Users on macOS can also try the following solutions below which has solved the problem for other macOS users:
For older macOS, try: downloading https://letsencrypt.org/certs/isrgrootx1.der Open the Keychain Access app and dragging that file into the System folder of that app. then find the ISRG Root X1 certificate in System and double click on it, open...
I'm just summarizing the symptoms and workarounds/fixes as far as I know, at least as far as Mac OS X goes. Staring Sept 30th 2021, Mac OS X 10.11 El Capitan (Fall 2015), Mac OS X 10.10 Yosemite (Fall 2014), and Mac OS X 10.9 Mavericks (Fall 2013)...