treequell I read over your link but I'm not sure I see any immediate takeaways. I've never used Apple iMessage. I don't know anything about "Google Chat Features" and following that link, I don't think it applies as I never used the Messages app. I opened it anyways on the previous phone but I didn't see the setting at all. (Fwiw, it was a Samsung phone.) I don't know anything about RCS in general. There are a few suggestions that are carrier related; I use US Cellular if you happen to know of any particular problems with them.
I would gladly use Signal only if all of my contacts also used it but alas that is not the case.