I don't know if I'm just trying too old versions. This is my attempt:

gem list ^puppet$

puppet (7.24.0, 7.23.0)

sudo gem install puppet -v 4.7.0

sudo gem install puppet -v 5.5.8

sudo gem install puppet -v 5.5.22

Done installing documentation for puppet after 11 seconds

gem list ^puppet$

puppet (7.24.0, 7.23.0, 5.5.22, 5.5.8, 4.7.0)

Then:

pdk validate --puppet-version=4.7.0

`pdk (WARN): This module is compatible with an older version of PDK. Run

pdk update

to update it to your version of PDK.`

pdk (ERROR): Unable to find a Puppet gem matching ~> 4.7.0.

pdk validate --puppet-version=5.5.8

`pdk (WARN): This module is compatible with an older version of PDK. Run

pdk update

to update it to your version of PDK.`

pdk (ERROR): Unable to find a Puppet gem matching ~> 5.5.0.

pdk validate --puppet-version=5.5.22

`pdk (WARN): This module is compatible with an older version of PDK. Run

pdk update

to update it to your version of PDK.`

pdk (ERROR): Unable to find a Puppet gem matching ~> 5.5.0.