Alright so I just checked after spinning up a windows server 2019 vm and installed plesk, looks like the earliest version you're able to go to is 5.6, and looking at the repo this basically confirms it that you can only go back to 5.6.
In either case, even if it was an option, considering that PHP 5.x hasn't been updated in a long time I would suggest avoiding installing it anyways and instead would recommend that you update whatever application you're using to bring it up to current version of PHP, or deploy using docker to try to minimize footprint.