I tried not to talk too much about 64-bit architectures, but that's a good point. Indeed not just Alpha but also MIPS R4000, UltraSPARC, PA-8000 were already around in the 1990s when the 32-bit kernel support got merged, while ppc64, s390x and TileGX hardware came a little later than the corresponding 32-bit ports.
For time_t, I remember it first getting discussed seriously among kernel developers around 2010 as it became clearer that we had misjudged how long 32-bit systems would be around for, how much work it would be to fix it, and how long before 2038 things would fall apart from bugs.
Before then, the general thinking was we could either delay dealing with it until the 2030s or 32-bit Linux would just not be there any more.
I would consider the LFS transition a user space failure, as glibc never made that the default and Debian still builds some packages with 32-bit off_t to avoid breaking the interface between libraries. As late as 2018, glibc was still merging architecture ports (csky) that default to a 32-bit off_t, despite the kernel having 64-bit off_t since 1994 (linux-1.1.46) before any non-i386 ports were added, and all new architectures in the kernel only supporting 64-bit off_t since 2011.
For time_t, I remember it first getting discussed seriously among kernel developers around 2010 as it became clearer that we had misjudged how long 32-bit systems would be around for, how much work it would be to fix it, and how long before 2038 things would fall apart from bugs. Before then, the general thinking was we could either delay dealing with it until the 2030s or 32-bit Linux would just not be there any more.
I would consider the LFS transition a user space failure, as glibc never made that the default and Debian still builds some packages with 32-bit off_t to avoid breaking the interface between libraries. As late as 2018, glibc was still merging architecture ports (csky) that default to a 32-bit off_t, despite the kernel having 64-bit off_t since 1994 (linux-1.1.46) before any non-i386 ports were added, and all new architectures in the kernel only supporting 64-bit off_t since 2011.