We are currently running ESXi 6.7 U3 and need to replace our SD Cards used for local storage due to VMware dropping support for SD cards in vSphere 7 (U3). Is there a method we could use to copy the ESXi installation onto a different local disk (i.e. M.2 SSD)? Or will we need to perform a new installation on all of our hosts?
There might be options to backup the configuration, then reinstall the host on the SSDs followed by restoring the backed up configuration. This could become tricky if advanced features are in place, e.g. NSX-T, in which case you'd need to install additional vibs prior to restoring the configuration.
Taking into account that the partitions/sizes in ESXi 7.0 change, and will largely differ between an upgrade to v7.0, and a new v7.0 installation, you may consider to reinstall the hosts with v7.0.