ZDoom

With the migration to the OpenGL 2D drawers, filtering is unconditionally turned off in software mode for UI elements in order to match the aesthetic of the game world - completely ignoring the user's selection for having it on in truecolour.

There's only the software truecolor linear filter, same as 3.4.x.

I can't tell if this is a bug report or a feature suggestion. Filtering is supposed apply to everything when it is turned on in the software renderer. If it doesn't, then that's a glitch.

I think you are using either Truecolor Softpoly or plain old Software Render (not truecolor), which don't support filtering.

To use filtering, you need to change your renderer to the Truecolor Software renderer (NOT SOFTPOLY) and then go into Display Options, go into the Software submenu and then into the Truecolor submenu, set all three options there to "On"

In legacy versions, After setting to software rendering the rifle is filtered, but no monsters are applied.