Not anymore. Here's what shows on their page:

> On Monday 24th August at 8PM EST, we received at letter from X Corp. asking to cease and desist the service XCancel. The service XCancel is stopped until further notice. We are seeking legal advice and won't share more details for now. Thank you for the trust you have put in these two years of XCancel.

Seems that xcancel.com is down now as well. Maybe they got C&D'd a bit later, or maybe they just took a bit longer to respond to the same notice.

xcancel worked even when nitter had problems before. I imagine they're running a fairly custom version of nitter now with their own workarounds.

Edit: I see it's not working either "Instance has been rate limited"