You can keep on hand a USB stick of your system-system your computer came with or last system with compatible firmware (until Apple adds a security update that actually bricks your USB port too)

All Apple security update are mainly 99% firmware add ons to brick 3rd party hardware and software developers, absolutely nothing to do with protecting you, the products you purchased or your privacy., in fact its Apple and some in congress you should be worried about.

So create a USB version of the system your computer shipped with or re download it in Recovery mode..issue with this is Apple messes with the installers as well, for example the installer for Majove now requires you to format the designated HD as AFPS!, imagine that, with out notice the system that was released before AFPS formats existed now requires this, and this is because Diskwarrior, etc can't save your data once Apple bricks your CPU or HD...

You can check the integrity of your EFI firmware using a terminal command; usr/libexec/firmwarechecker/eficheck/eficheck --integrity-check Terminal throws out no matching service found. either this system is not supported by eficheck or you need to reload the kext. Which is the error you would get if this was t2 mac, which it is not. Is something wrong with my Efi firmware?

Here is a link to firmware versions and clicking on them allows you to obtain the latest versions according to your Mac : enter link description here

You can keep on hand a USB stick of your system-system your computer came with or last system with compatible firmware (until Apple adds a security update that actually bricks your USB port too)

All Apple security update are mainly 99% firmware add ons to brick 3rd party hardware and software developers, absolutely nothing to do with protecting you, the products you purchased or your privacy., in fact its Apple and some in congress you should be worried about.

So create a USB version of the system your computer shipped with or re download it in Recovery mode..issue with this is Apple messes with the installers as well, for example the installer for Majove now requires you to format the designated HD as AFPS!, imagine that, with out notice the system that was released before AFPS formats existed now requires this, and this is because Diskwarrior, etc can't save your data once Apple bricks your CPU or HD...

You can check the integrity of your EFI firmware using a terminal command; usr/libexec/firmwarechecker/eficheck/eficheck --integrity-check Terminal throws out no matching service found. either this system is not supported by eficheck or you need to reload the kext. Which is the error you would get if this was t2 mac, which it is not. Is something wrong with my Efi firmware?

Here is a link to firmware versions and clicking on them allows you to obtain the latest versions according to your Mac : About EFI and SMC firmware updates for Intel-based Mac computers