last night I had to revert a site to a backup due to not being able to edit a page or post after upgrading to WordPress 5.3.
This morning I created a staging site at https://staging3.inolablueridge.com to test the upgrade process and locate the problem. As soon as I updated the same issue happened, with editing posts and pages showing a white screen. I went through my plugins and deactivated each one until I located the problem. The problem went away when I deactivated SmartCrawl Pro.
Please look into this asap as I need to get this site updated, as well as other sites. I have already activated support access onto this staging site.