Just to add (as I couldn’t edit my original posting), I tried switching off all plugins except for Really Simple SSL and then upgrading to 7.4. All the same errors appear. Updating the plugins made no change.
I then tried making the leap to 8.1 php and they pretty much broke everything. Even the admin panel for wordpress is showing line errors. The following are repeated a number of times on different lines.
Deprecated: Return type of WordPressPopularPosts\Container\Container:ffsetExists($key) should either be compatible with ArrayAccess:
ffsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in ******/wp-content/plugins/wordpress-popular-posts/src/Container/Container.php on line 50
Deprecated: Return type of Requests_Cookie_Jar:ffsetExists($key) should either be compatible with ArrayAccess:
ffsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in ***/wp-includes/Requests/Cookie/Jar.php on line 63
Deprecated: Return type of Requests_Utility_CaseInsensitiveDictionary:ffsetExists($key) should either be compatible with ArrayAccess:
ffsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in ***/wp-includes/Requests/Utility/CaseInsensitiveDictionary.php on line 40
I’m not sure how I can possibly isolate this. I switched off the WordPressPopularPosts plugin and it made no difference, as the error still showed. No idea what Requests_Cookie_Jar or Requests_Utility_CaseInsensitiveDictionary are.
Again, tried switching over the theme to something else, but it made no difference. Things seem to be seriously screwed here.
One last thing, the Goliath theme shows no updates available. I bought it quite a few years ago from what seemed to be a legitimate site. Now I see that site has vanished and I can’t upgrade.