Is a cleanout needed?

I am changing the standpipe on my washer. Currently it is outside of the wall and the trap has a cleanout plug. I bought a laundry outlet box that incorporates a drain pipe and it will bury the standpipe. This means there will not be an accessible cleanout at the trap.

Do I need to add a cleanout at some point to be up to code? I'm in Ontario, Canada, if that matters. Lots of videos and drawings do not show the use of a cleanout and has lead to a lot of confusion on my part.

The sewer line for this drain is about 46-50" away and it comes up vertically into the wall cavity. It runs under the basement concrete floor, diagonally to a stack about 7-8' away (the stack has a cleanout). The standpipe drain line would run horizontally after the trap and be joined to the vertical sewer with a T.