Sorry I should’ve written the full command and there was a typo in my post, == should’ve been =. 
If it were me, I’d probably do a fresh install of manjaro, update and then run the commands I used to install arduino. If it still doesn’t work without sudo… 
I think I know what is happening.
Found and hookup old arduino UNO. it is based on atmel m328p and using ftdi chip for ttl usb to serial translation. And guess what:
[lukas@lukas-20217 ~]$ ls -l /dev/ttyACM*
crw-rw---- 1 root uucp 166, 0 Dec 30 19:21 /dev/ttyACM0
[lukas@lukas-20217 ~]$
no root, no chmod and no udev. working like a charm 
my new arduino “variation”, SparkFun “improved” clone equipped with ATmega32U4 with direct USB controller.
the quotation from sparkfun page
The USB transceiver inside the 32U4 allows us to add USB connectivity on-board and do away with bulky external USB interface.
I think USB direct access permits have to be modified to solve the puzzle. can it be done?
I considered that, but I couldn’t find anything to say there was a difference, the stuff I did find lead me to believe there wouldn’t be. I couldn’t test here and I thought you’d mention if you had another board. 
Did you see/run the linuxarduino-setup.sh that came with the web version?
That has some udev rules in it, from the names it didn’t look like any applied, but you never know.
Not sure they’d help though, the permissions are already shown as correct.
I notice the file but it wasn’t mentioned in the install instructions. I assumed that the file is executed as a part of install.sh file.
Just checked install.sh. there is jump to linuxarduino-setup.sh, but is hashed. will try to experiment with it in the new year. 
btw. Happy new year whatever you have it already or waiting for it :).
That means it is commented-out…To un-comment it, remove the hash infront of it.
I know that much 
. after more then 15 years in IT :). let say I had my first computer (PC DOS) when MS Windows 3.0 was introduced
Ok i can’t look into ones mind ofcourse, i just placed it on table just in case 
I dropped pro IT about 12 years ago. I’m pretty rusty :). At the end I was glowing from cathode tube monitor radiation :). Mostly hardware and support, some networking, Now learning new tricks from you guys. thank you for support 
Awesome! Simply adding myself to uucp solved everything, including serial monitor. I used the arduino-ide-beta-bin 2.0.0.beta.11-1 and it worked pretty much out of the box on Kernel 5.13.15-1-MANJARO.