The first page in each ROM thread "Installing with TWRP" section gives a link to the common TWRP topic, From there there's a link to go to a collection of available TWRPs. From there, it shows Garnet last had files added June 30th of last year. There's two files. OrangeFox and twrp. The twrp one is for Android 12(HyperOS is Android 15, so decrypt won't work). I don't know anything about OrangeFox.
It's not Xiaomi.eu's responsibility to provide recoveries for us. It's amazing that they give the resources they do to reduce how much hunting we have to do. If the TWRP and OrangeFox provided on the SourceForge page aren't what you are looking for. You'll need to look independently. If you find one that works, notify that TWRP thread so they could get the collection updated. If no one has made a recovery for Android 15 for Garnet, go ahead and create one and notify in the TWRP thread about it's availability.
If none of that works for you, you can always use fastboot update.