Just pickin' nits ...
My original intent was to disparage the use of 'protestant' when referring to someone that is not Catholic
(ain't gonn'a go there to Jew or Budhist or whatever)
I understand. I’m really trying to figure this out with you.
If Fundamentalist is something you feel is too easily denigrated, I can see that.
Biblicist is good except for the reasons I listed earlier mainly because it is usually taken to mean the same as Fundamentalist and would have the same problem.
Maybe Scriptural Christian? Or Bible Christian. I’ve seen “Bible Believing” used to describe churches and “non-Denominational.” Maybe one of these will work for you. I’m guessing you’re not a church “member” so maybe not.
It’s not my choice of course, but I still think “not Catholic” and non-Catholic” have the same drawbacks as “protestant” in that they refer to Catholicism when I think that’s what you wish to avoid.