Since "upgrading" to OS X 10.15.6 I have similar problems with Safari. (MacBook Pro, Retina, 13-inch, Mid 2014). Other browsers work fine, with caveats, see below.
Catalina upgrades are likely to affect Safari because it is a core conduit for the eventual integration across all Apple operating systems.
Apple's O/S software testing has been poor since the introduction of Catalina. They don't do a great job of keeping software partners up-to-date on changes that affect them, e.g. Evernote. As of 2020-06-21 Web Clipper prevents this error message after failing to upload from Safari.
Clipper has encountered an error
Unknown error occurred.
EDAM/ENML_VALIDATION
Element type "embed" must be declared.
Copy Logs
Apple currently uses customers and software partners as beta testers (not just my opinion.)
Google Chrome is based on an open source code project called Chromium. This platform is used by Microsoft Edge, Opera, Vivaldi and other, popular browsers. The Chromium engine features a "Renderer" applet for each connection between a browser plugin and an external server. If you use Evernote and have seven tabs open, you will have (at least) seven Renderer applets. They consume tons of memory, and make enough heat to turn on your fan. The link below has more info.
https://medium.com/@evasamsonoff/stop-google-chrome-helper-from-eating-your-cpu-in-2019-the-fast-way-91fb68a538c2
Safari and Firefox use their own code. Firefox supports Evernote (and Zotero). That's where I've gone for research projects, until Safari is back online.