Open https://app.element.io
The text is unreadable in either theme/

Element itself has a choice of light or dark theme so Otion should not be doing anything to the page.
If I try in compatibility mode (and in previous versions) the page works.
The extensions I have are uBlock, 1password - I used to have Dark Reader but this is turned off.
Orion should not alter the page.
Version 0.99.128-beta (WebKit 619.1.11.111.2)
Sonoma (14)