"Unused RAM, is wasted RAM" - Generally Accepted Truism.
I wouldn't be remotely concerned about how much free RAM you have on an Android device.
Android has always been extremely efficient in it's RAM management.
Having more, or less free RAM is virtually meaningless.
Clearing RAM manually, only briefly increases the amount of free RAM, and serves no real purpose. If anything, you'll just be using the battery for nothing.
OCCASIONALLY, you may have a misbehaving app, which MIGHT cause an increase in it's RAM usage, but that's definitely not typical.
One of the purposes of RAM, is to keep currently being used apps in a "quick access state", which gives the user the real feeling of high performance.
Clearing RAM, will just be used again to improve the performance of your device.
Unless your device has lag, or other performance issues, just forget about RAM usage. 😊
You're referring to the "libfs_mgr", right?
That's likely just because the Recovery is checking for an external sd card, which your device does not have. It's not actually an error.
Errors in Recovery are almost always in Red Text, just FYI, so if it wasn't in red text, don't worry about it.
It's perfectly normal / expected & intended that when you Boot a device into Recovery that it runs some system checks.
It's not necessary for Samsung's Devs to use a recovery specifically for each different model. So you may see a brief bit of information, that is of no concern and nothing to do with any issues.
If you are concerned about the performance of your device, then I'd suggest that you backup your device with Smart Switch and Factory Reset.
I, along with other, ALWAYS Factory Reset after EVERY Android Version Update, and I have never, ever had any issues whatsoever following this routine.
Why I Factory Reset:
Thank you RedDogRabbit.
Hi, as suggested by RedDogRabbit, kindly back up and factory reset your device by following the steps in the given links.