Schwab says my Safari browser is not updated. I’m using 17.3 . What do I do?

For security, financial and other Institutions and often require that customers use computers that are both using a current/supported version of the computer's host Operating System - and secure version of web browser software.

Be aware that some websites may incorrectly identify your iOS/iPadOS Safari User Agent or version when used in one or other of its browsing modes - of which there are two - these being Desktop and Mobile. Misidentification of the browser Agent can often manifest as the website reporting that your browser is out of date, or won’t properly render a page. This may be your problem.

It’s easy to switch between modes if a website isn’t functioning correctly. From the desired web-page, touch the aA icon at the left of the Address Bar; this will reveal a menu. From the menu select Website Settings, then select (or deselect) Request Desktop Website, then tap Done. Now refresh the webpage.

The chosen setting will be saved for the selected website - and can be simply reversed if needed.