I am running php shopping cart for years, just updated my server and is only has php 7.4 and above.
Does anyone know of a cheap cpanel host that still has php 5.6 option
Most CloudLinux based still have alt-php56 basically a hardened version of PHP 5.6 but to be completely honest with you, If this shopping cart you have for years doesn't have an updated version now that PHP 8 is even out, you might even consider a migration? I understand migrating is an undertaking sometimes but PHP 5.6 is eons to old, and out of date even if CL provides a hardened version which is being security supported.
In any case, most CloudLinux based servers will support it, but like stated above you may consider migrating or upgrading if the vendor has given a new version