I am currently using Houdini 20.5.579 and it seems that packages/SideFXLabs20.5/misc/labs_ocio has disappeared since Houidni20.5. So I set it myself to Documents/Houdini_Configs/studio-config-v2.2.0_aces-v1.3_ocio-v2.3.ocio and also Houdini.env OCIO = "C:/Users/UserName/Documents/ Houdini_Configs/studio-config-v2.2.0_aces-v1.3_ocio-v2.3.ocio". When I launch it, it seems to be in there, but when I try to switch the View Transform in OCIOSettings, I get an error like the one in the image below: even if I re-launch Houdini and change the View, the changes are not applied and it goes back to Un-tone-mapped! I am trying to change the View Transform to a new one and getting the following error. What should I do? And what version of ACES are you guys using?

First of all, no need to set it in the packages with a .json AND in the houdini.env file. Setting it at one points is enough. I'd suggest the packages method. Simply paste this in a new text document, change path accordingly and then rename it so the file extension is ".ocio"

{
"env": [
{
"OCIO": "YOUR_PATH_HERE/config.ocio"
}
]
}

Second, that's not an error you get but just a warning. It just means that the current viewer does not immediately adapt the settings and you either have to open a new viewer tab or restart Houdini for the changes to take effect. If I understand you correct you want the SDR Video view transform as your standard?

Get this OCIO config: "cg-config-v2.2.0_aces-v1.3_ocio-v2.3.ocio" (You most likely don't need the studio config)

Open it in a text editor and change the line that says: "default_view_transform: Un-tone-mapped" to
"default_view_transform: ACES 1.0 - SDR Video"

That should get you going.