This is the output of the install script:
root@myserver:~# curl -s https://install.zerotier.com | bash
*** ZeroTier One Quick Install for Unix-like Systems
*** Tested distributions and architectures:
*** MacOS (10.7+) on x86_64 (just installs ZeroTier One.pkg)
*** Debian (7+) on x86_64, x86, arm, and arm64
*** RedHat/CentOS (6+) on x86_64 and x86
*** Fedora (16+) on x86_64 and x86
*** SuSE (12+) on x86_64 and x86
*** Mint (18+) on x86_64, x86, arm, and arm64
*** Please report problems to firstname.lastname@example.org and we will try to fix.
*** Detecting Linux Distribution
*** Found Debian "buster", or "sid" (or similar), creating /etc/apt/sources.list.d/zerotier.list
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
*** Installing zerotier-one package...
This install buster repo, not bullseye one.