I made an update for WordPress 5.6.
The website was running ok but there was a problem with the main website, where I have slides with Slider Rev.
As to main site, the logo was only visible and the rest of the screen was white.
The web content was working ok (despite difficulties with menu) and all other stuff as well.
I could not find a reason for that, so quickly downgraded to WordPress 5.5.3 and it works ok. I did not test how it works with PHP 8.
Can you confirm if we can update for W5.6 and PHP safely?