Hi. I installed the latest Manjaro Linux 26.1 test version with KDE Plasma. After a while I found out that the Linux kernel does not support scx profiles, so I will not be able to use them in the popular Falcond GUI. Is it specific to this Manjaro test version that the kernel does not support scx? I think that in the stable version of Manjaro, scx worked for me in the Falcond GUI.
Welcome to the forum. What exactly are SCX profiles?
Also this might help.
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I have no idea what exactly those schedulers do and how they are configured, but they certainly seem to be available - for every newer kernel there is an optional dependency scx-scheds. Install it and try again whatever you are trying.
He’ll probably also need to install scx-tools — I haven’t checked the dependency chain, but it’s in the repo. 
scx-tools will install scx-scheds as a dependency:
❯ pamac info scx-tools scx-scheds | grep -Ei 'name|depends'
Name : scx-tools
Depends On : libgcc glibc polkit scx-scheds
Name : scx-scheds
Depends On : bash bpf libgcc glibc jq libseccomp libbpf libelf
If I am understanding your topic correct, you can check
$ zcat /proc/config.gz | grep CONFIG_SCHED_CLASS_EXT
CONFIG_SCHED_CLASS_EXT=y
As pointed out by other members you may need to add the necessary tools.
Tweaking kernel parameters for response time consistency - Gaming - ArchWiki
it is recommended to test different schedulers as described in Improving performance#CPU scheduler. For example, the scx_cosmos scheduler from scx-scheds shows promise for improving response time consistency, as it optimizes task-to-CPU locality (enhancing cache hit consistency between runs), reduces locking contention, and is suitable for general usage scenarios, prioritizing interactive tasks under load. Similarly, scx_lavd is specifically optimized for consistent gaming performance. You should test different schedulers to see which is the most successful for your workload.