I've updated the web page with words "All versions 2.0.4 and later are supported. Versions 2.3.0 or later are recommended, due to improvements in Boards Manager." I also changed "2.0.x" to "2.x.x".
Arduino added the ability for a "pre-uninstall" script starting in version 2.3.0. All the Teensyduino packages were updated to include that script. It's not a big deal for MacOS and Linux, but really helps avoid some unpleasant problems with Windows.
Very old versions 2.0.0 to 2.0.3, and the many pre-2.0 betas, are no longer supported since we switched to ZSTD compression (first supported in 2.0.4) which really speeds up download and install times.