6.6 is the newest you’ll get on Debian with backports (for v12) or testing (trixie, future v13). You’d have to go to Sid, and even then it’s only 6.7 at the moment.
I’d avoid Sid (aka unstable), unless you really want to test things out. It’s known as unstable for a reason. If you really want a newer kernel & packages, I’d look at another distro, Debian is famously (notoriously?) slow to pull in updates, since stability is one of the major requirements, even testing is quite stable most of the time.
Yes. I know. I have some experience with Linux
I moved from Debian 12 to Testing. I had some small issues with dependencies, but all sorted out.
Xanmod 6.8.8 is running fine, for now.
I’m unfamiliar with Xanmod kernel. You’re making me interested, I was originally just going to run Debian testing installed on ZFS root (see Debian Bookworm Root on ZFS — OpenZFS documentation), which I’ll just set the sources to testing, rather than bookworm, when doing the install.
Also a good idea to pin Chromium and Firefox to unstable (also suggested in the link I provided). Firefox and Chromium in unstable track upstream releases pretty closely - the maintainers are very fast to upload new versions.