I'm still running mine with 5.4, so I'm not entirely sure on that. But what I am sure of, is if you get your own VPS, multiple instances of PHP can be set up.
You can get a cheap VPS for $28 USD per month:
https://www.knownhost.com/managed-vps.html
My server's default PHP is 7.2, which I'm using for newer products such as Xenforo & Wordpress, but my vBulletin 3.8 is set to PHP 5.4.