without a reddit account:

... can you also force Siri off by using Screen Time controls? I noticed that in the Screen Time menus, "Content and Privacy" restrictions can be toggled on. From there seems to be an additional "Siri" menu that lets me change the allowed Siri version from Siri Classic to Siri AI as well as options to turn off the global writing tools/assistance (which turns off the annoying Siri bubble on every textbox now).

I suspect forcing Siri off via those controls would work easier than using Low Data Mode or trying to force Siri to disable via language selection.