I wasn't around then, but I would be surprised if that description of TiVo's actions is accurate. I'm more inclined to believe the blog post from the person who "led the GPLv2 enforcement effort against TiVo" than the definition of tivoization that exists in the popular consciousness, which I expect is a political invention of the community over time. The article says "At the time, TiVo was doing the right thing in providing what the GPLv2 requires — including the ability to reinstall GNU and Linux software onto the actual device" and "TiVo never prevented such reinstallation". There is a whole section "How Discussion Focused on Cryptographic Lockdown Generally" about where the cryptographic lockdown worries came from; it was years after TiVo, during the GPLv3 drafting process. They even link to resources about how to update Linux on TiVo devices, one of them mentions breaking the "encryption" involves modifying the "tivoapp" userspace binary in a way that looks to me like disabling checking of the Linux kernel hash.
Linus is saying that signed Linux kernels are a good thing (and I concur), the situations he was describing there are for Secure Boot based systems, which are explicitly designed to allow for software freedom. IIRC this happens in a couple of ways:
1. the UEFI firmware requirements set by Microsoft require the ability to disable Secure Boot, and ISTR also require or encourage the ability to enroll secondary keys.
2. the shim firmware built by a distro and signed by Microsoft and booted by the UEFI firmware allows a physically present user to enroll secondary keys, and then all the layers beyond shim support verifying things using those keys.
Of course Microsoft controlled Secure Boot isn't the only kind of cryptographic lockdown in use today. The method used on mainstream Android phones is different and I don't know the details but I think it allows wiping the phone and then booting unsigned Linux kernel builds but I don't think it allows the MOK style setup from the PC UEFI world. The Apple M1 devices have yet another system.
Linus is saying that signed Linux kernels are a good thing (and I concur), the situations he was describing there are for Secure Boot based systems, which are explicitly designed to allow for software freedom. IIRC this happens in a couple of ways:
https://wiki.debian.org/SecureBoot#MOK_-_Machine_Owner_KeyOf course Microsoft controlled Secure Boot isn't the only kind of cryptographic lockdown in use today. The method used on mainstream Android phones is different and I don't know the details but I think it allows wiping the phone and then booting unsigned Linux kernel builds but I don't think it allows the MOK style setup from the PC UEFI world. The Apple M1 devices have yet another system.