I tried Goldstar, LG, and RCA, no luck there.
The only way I can find to get to #749, is to add a TV, then scan
all codes. I did not see anything close to #749.
I guess mine was produced before that TCL 55US57 was
added to the database. Sure wish I could update the remote.
I guess these "roku tvs" are less than optimal for setting up
one of these remotes? Thanks for the input!

EDIT: I read what I could find till I remembered most of what
I needed to do to set up the RC50. Just went with learned
commands and macros.