Hey!
I just created this account to let you know, I believe I found a fix for the greyed-out RAM Plus option in Noble 2.9. (Maybe it also appeared in previous versions, I just installed 2.9 on my S9)
I've followed the YT video linked in the release notes, on how to enable RAM Plus with the SetEdit app. After I completed and restarted the phone, RAM plus appeared under the Memory options but it was greyed out and I couldn't change values. After a few minutes of searching I didn't find any fixes so I downloaded SetEdit to my S22 Ultra, where RAM plus is working, and I've found out that the ram_expand_size under Global Table is not a list, just ONE specific value, in the tutorial it was like this "ram_expand_size" "2048,4096,6144,8192" and "ram_expand_size_list" "2,4,6,8".
Now the latter is the same on my S22U, but "ram_expland_size" only contains one value, in my case it's 6144. I jumped back onto my S9, changed said key to only one value, 6144 as well, (deleted the other 3 values from the string) and after a reboot it was working. Checked ThunderTweaks's Virtual Memory menu, and the Swap size is changing according to the value I set.
If it's a known fix, pardon me. It's possible someone found this way earlier, I just couldn't find it in those few minutes I was searching for it. Also I'm fairly new to this kind of stuff, my S9 was sitting in a drawer for almost 2 years and now I decided to give custom ROMs and Rooting a go. I'm looking forward to what I can achieve with it.