I will continue to update this article with new information as it is available
I have updated the presets that come with my eBooks to include 7.3 versions. I am continuing to work on creating versions for the standalone presets
It turns out that I was wrong, and you can continue to install older presets as normal. Lightroom will detect new presets added to the legacy folder, and will upgrade them at launch. I have updated the article below to reflect this.
Lightroom 7.3 and what's changed
Adobe has just released a major new version of Lightroom that includes some significant changes. The biggest and most notable one is the inclusion of new Raw and “Creative” profiles. However, there are also some major changes under the hood. Specifically, they have changed the file format that presets use.
Previously Lightroom used the .Lrpreset format. It now uses a more standard .xmp file format.
If you have any of my guides or presets, you may be wondering what happens.
If you are upgrading and already have presets installed, Lightroom will upgrade the presets for you when you first launch Lightroom 7.3.
If you wish to install older presets after you upgrade, you simply put them into the original presets folder and when you restart Lightroom, it will upgrade the newly added presets. It's important to make sure you only add .lrtemplate files to the develop presets folder, and only .xmp files into the settings folder.