I may have posted about this somewhere with a pretty similar title, but I can't find it, and I don't remember it getting anywhere so it doesn't matter.

Currently, I'm on Manjaro with i3-gaps on an HP Pavilion g6 with Linux kernel 5.20.

I've tried a bunch of distros and the only one I remember working is Fedora 29, and only with Plasma.

Welcome to LQ!. A thread discussing the same issue here (in particular post #5 onwards)
https://bbs.archlinux.org/viewtopic.php?id=243305

What you need to know is that there may be a choice of input device drivers available, and the OP in that thread mentions the use of the 'synaptics' Xorg input driver. Wherever possible 'libinput' should now be in use by default, but there may be some hardware that is still better supported by the deprecated 'synaptics' driver. Post #6 contains a solution based on that driver.To complicate matters some desktop environments (in Xorg environment) will only work properly with the the libinput subsystem, and Wayland completely relies on it now.

Please let us know how you get on.

From my understanding, I need the Synaptics driver, right? So when the Manjaro (Architect) installer asked me for X.org related packages, I did pick xf86-input-synaptics. Isn't that the Synaptics driver? And doing the xinput thing from the fifth post, I get "property '121' doesn't exist, you need to specify its type and format".

To see which input driver is currently in use do
and report back here.

BTW, this will only be applicable if using an Xorg-server, and not Wayland.

There's various stuff for the screen or the power button, probably not important here. It says that for the trackpad, I am using the Synaptics driver.

I'm definitely not on Wayland as well.

Read #6 of the thread I linked to.

Property '148' doesn't exist either.

Run the following to get the device ID for you trackpad
then do
*Use the device _ID pertaining to your trackpad

That will show you the available properties (functions) and their property ID's as well.

When you want to make that permanent, you can use the custom Xorg configuration file as per post #6.

Alright so I have a list, and the property Coordinate Transformation Matrix which is currently set to 39, 88 has an ID of 150. So I replaced those commands from the Arch Forum, and this time I get no output, and it doesn't even change anything. Now what?

Which desktop environment is in use? I’m wondering if just using libinput would be better here? (That would require removing the Xorg synaptics package (or at least removing/renaming the synaptics config file).

I'm using the ratpoison and openbox window managers. And in order to remove the Synaptics driver would I have to reboot? Cause I'm trynna get long uptime

No, you'd just need to restart the X-server (usually CTRL+ALT+Backspace twice).

Instead of removing the synaptics driver package, you could just rename 70-synaptics.conf eg
then restart the X-server.

To check if libinput is then in use run the first command given in post #4 again, and check touchpad behaviour again.