Here is the last beta of Blocs 5.0.2 (which will officially ship on Monday). The main fix in this release is the WebP issue on Catalina.
Unfortunately the best fix I can find without getting wrangled up with additional JS is to default background-image for Safari to jpg/png. Chrome will still take advantage of WebP when used via the class rule background-image.
(WebP will continue to work in Safari as normal with image tags.)
Maybe we can revert things back once Apple drop security support for Catalina. If it’s still a major concern then I can add a pref in somewhere to enable/disable Catalina WebP fallback.
Anyway, happy testing and have a great weekend!
Don’t forget to hard-reload the page to clear cache
I believe Apple has already dropped security support for Catalina. They stopped with Mojave over a year ago when Monterey shipped and Apple’s normal practice is to drop the next oldest version as soon as a new version ships, which in this case was Ventura.
If you look at the link below there were security updates for Big Sur, Monterey and Ventura on the 24th of October. Nothing for Catalina.
If you scroll down further to the 20th of July there were updates for Catalina, Big Sur and Monterey.
I think this is a good solution too. I just verified my affected webp web site is now viewing well in Safari using MacOS 10.14.6 and 10.15.7. I even had an old MacOS 10.11.6 system that I could load and it’s viewing well in Safari there too.
Blocs 5.0.2 Beta Build 2 
