Older sites may encounter some issues with WordPress 5.5 and older plugins using the old JQuery. It also appears many plugin developers simply weren't ready so updates are breaking sites. Folks, wait a bit, I know it's hard to see a lot of updates, but just because an update is available doesn't mean it's a safe update. Always backup prior to major updates like this one.
Two issues related to WordPress 5.5 are possibly affecting thousands of websites. This is how to fix them.