I got this fix 5/24/22 it's similar to many others. They don't work this one does. It's from a LG engineer.
Put the affected LG phone in airplane mode by pulling down the notification shade and tapping on the plane icon.
Putting the phone in airplane mode should stop the IMS error message from popping up.
Open the phone's settings and tap on Apps and Notifications, followed by App Info.
On the App Info page, click on the three-dot menu icon in the top-right corner of the screen and tap on Reset App Preferences, then tap on Show System.
Look on the app list for "com.lge.ims.rcsprovider" and tap on to open the next page. Doing so will pull up the pre-installed IMS provider app's detailed overview.
Once there, tap on the clear data/cache option, then clear storage, then force stop.
Then restart the phone. If the pop up happens anytime during this. Restart phone and do again.