If you rebuild your VPS I suggest going with a better panel like Virtualmin instead, but you still need to install PHP 8.0 or 8.1 manually. Your VPS is on PHP version 5.4.16 which is old - really really old, no longer supported by PHP (neither is 5.5, 5.6, 7.0, 7.1, 7.2, or 7.3 now) and contains several security vulnerabilities (the last version of 5.4 was 5.4.45 released in 2015). Significant improvements to PHP were made with version 7 and then version 8, version 7 represented a massive increase in performance and a decrease in server load compared with 5.6, and version 8 comes with a JIT compiler to further increase performance and further decrease server load compared with 7.x. You can see the results of this from published benchmarks.
Regardless of which control panel you're using I recommend adding a trusted php repo which maintains the latest builds. With uBuntu you can use Ondřej Surý's one and on RHEL/CentOS etc you can use Remi's. After you've installed the repo your OS will be able to offer you the latest PHP builds in the branches you have installed when you search for package updates (for example 8.1.xx which is currently at 8.1.5). Make sure you install the new branch that you want before you uninstall an older one.
Good luck!
