As shitty as it is, it's nice of Lenovo to at least make it easy to enable the second CA. I wonder if all OEMs will be as "nice", or if any will require you to boot into Windows just to edit the EFI variables to add the second CA.
Edit: Also, I've read a few horror stories of systems no longer displaying anything after the UEFI CA was removed from the trusted CAs, because there was no iGPU and the discrete GPU required an OpROM. No display meant no way to boot into the UEFI firmware to revert that change or even disable SB. How is that not a problem now?
There used to be a requirement by MS mandating secure boot to be disable-able. Though I think they scrapped that requirement later on. No idea if third party CA enabling also has such a requirement.
Disabling secure boot is one thing you should be able to do with hardware you own. Of course that's not a good idea if you want to run a non-Windows OS in a secure manner. Installing your own CA cert should also be possible. That's what we do at work with current UEFI implementations.
On the early Surface Pros at least, you had to boot into Windows and run a PowerShell script to enable the MS UEFI CA certificate. These days it looks like they made it a option on the system firmware.
Edit: Also, I've read a few horror stories of systems no longer displaying anything after the UEFI CA was removed from the trusted CAs, because there was no iGPU and the discrete GPU required an OpROM. No display meant no way to boot into the UEFI firmware to revert that change or even disable SB. How is that not a problem now?