I find cannot share screen on WIndows XP today

Yes, officially Windows XP has been stated as not supported for quite some time. Note however if you attempt to join a meeting using an XP device, Zoom will offer to download a client installer for v. 5.0.5 as a file named 'ZoomInstallerXP.' And if you download it, it will install. And you can use it to enter a test meeting (at https://www.zoom.us/test). That is all true as of the date of this reply. One might well wonder why this would be all be the case if Zoom had entirely abandoned XP way-back-when.

Mid July, 2022 I used an XP SP3 device + 5.0.5 to successfully join a Zoom meeting. However in joining a meeting earlier today (early October, 2022) using XP + 5.0.5 I had no audio (despite the menu option 'Test speaker and microphone' incorrectly confirming that audio was functioning correctly). Also, after about 2 minutes, I was thrown out of the meeting and received the message 'Network connection failure. Please check your network and try again' (even though my wired network connection was rock-solid). These two issues replicated & persisted.

My interpretation of all these events is that (1) Zoom had been continuing to allow for use by XP devices 'on the down-low,' while skirting any official support to XP users and (2) these two issues (that apparently emerged mid-August 2022) are XP-specific and Zoom, given its current market situation, has decided not to devote any more resources to coding server-side XP workarounds. So, practically speaking, no more Zoom under XP. They ought to at least take the time to delete the ZoomInstallerXP offer … and have Zoom return messages like 'Zoom will not run under your OS" instead of letting you actually enter meetings.

You CAN enter a Zoom meeting under XP using the 360 Extreme Explorer browser, v. 13. First you have to cancel-out of pop-up offers to download ZoomInstallerXP (that would simply reinstall 5.0.5) and also to launch the Zoom client. Then there will be a link stating "Having issues with Zoom Client? Join from Your Browser." Click that link and, after a slight delay, you will be able to access the meeting with audio & video. But it will consume nearly 100% of system resources and will bog XP down so much as to make it – and your presence in the meeting -- non-functional.