Why is second hd auto mounting and by what mechanism

I am running manjaro on a system with an ssd and hdd. I installed on the ssd and it shows up under sda
The ssd is under sdb. Some how it is mounting but is root for user and group permission and is read only.
I have looked at fstab and it only has 3 entries, /, swap, and /tmp.

When I do any kind of google search I get things related to auto mounting that say to put the entry in fstab. What I want is to know why they heck it is auto mounting and what textual files I can view to explain to me the operation of the system. As it is this feels like the 90s all over again trying to use linux and I have used it for a long time. Don’t understand why the info is not out there and easily pulled up with a search query.

What the heck is mounting the drive? What specific files and locations can I look at. I delved into systemd as well and found nothing.

Are you sure it’s actually mounted?

You can see that by a simple lsblk command, just after booting.

It might only be mounting it when you try to access it from the file manager.

Automounting is usually configured through fstab or systemd.
Also automounting is done by root, so that mounting point is owned by root until you change its ownership.

lsblk returns:

loop0    7:0    0  96.6M  1 loop /var/lib/snapd/snap/core/9804
sda      8:0    0 465.8G  0 disk 
├─sda1   8:1    0   457G  0 part /
└─sda2   8:2    0   8.8G  0 part [SWAP]
sdb      8:16   0 931.5G  0 disk 
└─sdb1   8:17   0 931.5G  0 part /run/media/myUserName/my1TB_drive

The sdb1 appears to be auto mounting on startup. I need to find out what is doing this so I can stop that and do the mount in fstab with my username and group. If its systemd where would that file live? I delved into that with ubuntu at one time but you do it once and it works and you forget for next time. Back to my google foo.

I don’t have any entry in my fstab for this drive. Here are its contents:

# /etc/fstab: static file system information.
# Use ‘blkid’ to print the universally unique identifier for a device; this may
# be used with UUID= as a more robust way to name devices that works even if
# disks are added and removed. See fstab(5).
UUID=b3b17c2f-2aa1-4f71-8b87-40ad33005635 / ext4 defaults,noatime 0 1
UUID=e18f1de9-3d4d-44f3-995d-4886a4193179 swap swap defaults,noatime 0 2
tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0

If it is systemd doing this where should I look. I did some cursory looking at systemd locations but I was unable to find a file that was mounting things.