One of the things that's quite popular with people out in the world is being able to set up a Linux server and then leave it be for the better part of a decade without having to reinstall it or upgrade the distribution. I believe this is a significant reason people used CentOS, and it's popular enough to support similar things in other distributions. I'm not fond of these old zombie distribution versions, but even we have some of them (running CentOS 7). However, I'm broadly pessimistic about people being able to get this for free in the future (cf), and I'm also pessimistic about even the current five year support period you get for things like Canonical's Ubuntu LTS releases. To put it one way, Red Hat's move is not unique; Canonical is monetizing Ubuntu too.

The reality is that reliable backports of security fixes is expensive (partly because backports are hard in general). The older a distribution version is, generally the more work is required. To generalize somewhat, this work does not get done for free; someone has to pay for it.

To date, this public good has broadly been provided for free for various periods of time by Debian developers, Red Hat, Canonical, and so on. Red Hat's switch from 'CentOS' to 'CentOS Stream' and now their change to how Stream works marks Red Hat ceasing to provide this public good for free; it's now fairly likely to be a more or less private, for pay thing. Canonical has never provided this public good beyond five years (and in practice only to a limited extent), and now there are signs they're going to limit this in various ways (also). Debian has sort of provided this only semi-recently, in the form of non-official five year support (and extended paid support). I'm not sure about the practical state of openSUSE but see their lifetime page for the current claims.

(Oracle claims to provide extended support for free but I don't trust Oracle one bit.)

People using Linux distributions have for years been in the fortunate position that companies with money were willing to fund a lot of painstaking work and then make the result available for free. One of the artifacts of this was free distributions with long support periods. My view is that this supply of corporate money is in the process of drying up, and with it will go that free long term support. This won't be a pleasant process.

The whole thing is why I said that people who wanted a decade of free support would need good luck. Maybe a way can be found to squeeze through the roadblocks that the people providing the money are trying to throw in the way (and the money will keep flowing, because one end game is that Red Hat and Canonical exit the long term Linux distribution business).