Twitter is now banning links to Mastodon, Post, Facebook, Instagram, and banning other linktree type links https://help.twitter.com/en/rules-and-policies/social-platforms-policy
Promotion of Alternative Social Platforms Policy | Twitter Help

This is just sad and pathetic, tbh, lol
@parkermolloy
As suggested by others, there's still the QR code that can be attached to a tweet or even used as one's profile avatar.
https://www.qr-code-generator.com
QR Code Generator | Create Your Free QR Codes

QR Code Generator for URL, vCard, and more. Add logo, colors, frames, and download in high print quality. Get your free QR Codes now!