Can't turn off spell checking in Messenger

Thanks Tom Gewecke, the problem is now solved. I was going to re-download the app from both the App Store and Facebook, but it seemed like I had to install it when I downloaded it from the App Store so I did, and then I had the missing options with all three turned off and didn't have the unwanted spell checking anymore. It was your perhaps unintentional suggestion that I re-download the program that did the trick.

Thanks, but that's what I said: "System Preferences (Settings) > Keyboard > Text input > Input Sources > Edit > Correct spelling automatically". That's turned off and was turned off when I first went there to fix this. I can try toggling it... but that doesn't help, I have the unwanted red underlines whether the setting is on or off. The setting apparently doesn't apply to Messenger so I suppose it doesn't apply to other apps as well, whether it's said that it does or not. But it seems strange, not being able to turn it off. I just now tried the systemwide setting on my iPhone and it does work with Messenger on that – but apparently not in Ventura on my MacBook Air.

You scared me there, as I had to think, "Did I not check Messenger preferences?" I had, but the three options below choice of language didn't appear when I did, and they still don't. Could this be because I have "System Language" selected rather than "English (US)"? Let's see... There's no immediately visible change, but it says I have to restart the app. I'll do that... They still aren't there. I'll turn off the wifi, shut down and reboot... Still not there. I already sent this in to Messenger, but there are two Messenger forums on Facebook and I'll write about this problem in these, thanks.

P.S. Unfortunately the Facebook groups called "Messenger" and "Facebook Messenger App" consist of trash having nothing to do with the program, so I'm not going to get any help there and the problem remains unresolved. I don't suppose anyone seeing this knows how to make the three missing options appear, but thanks anyway.

Thanks. I resubmitted my problem report to Messenger with your screenshot and mine of the same window.

Thanks Old Toad. I booted into Safe Mode, the setting was still off and I still had the problem, but then I re-downloaded and installed the app from the App Store, which corrected the problem.