All you need to know is right there in that line
shipyardguy wrote: ↑
Sun Jun 16, 2019 1:12 pm
Please upgrade to PHP equal to or greater than 5.4.7 but less than 7.3-dev in order to install or update to phpBB 3.2" Currently have PHP 7.3.6
7.3.6 is higher than 7.3-dev
Just downgrade the php version to 7.2.x and it'll work.