Wordpress works just fine on lower php versions, it is not a requirement to have a higher php version, version 7.3, which we offer, is currently the recommended one however.
https://wordpress.org/support/article/requirements/ said:
Note: WordPress also works in legacy environments with PHP 5.6.20+ and MySQL 5.0+, but these versions have reached official end-of-life and as such may expose your site to security vulnerabilities.
There is no option to gain ssh access on shared hosting (free or paid) to that level, to be able to fully control php version you would need to purchase a VPS.
There is no hosting account associated with the forum account you post from so I can not help troubleshoot for you.