The pollster must be rated at-least 2.5 stars on 538's pollster ratings
https://projects.fivethirtyeight.com/pollster-ratings/

The poll most provide enough information to be able to calculate what the average approval rating were be if Democrats polled were to be excluded from the average.

and obviously I have to be made aware of it (and be able to access the full detailed results needed for above calculation). I might miss a just a one off poll where this barely happens so please comment it here if you want a guarantee that I am aware of it.

Example: In this Gallup poll he came pretty close
https://news.gallup.com/file/poll/328649/210118TrumpFinal.pdf
which gives a 46.8% average disapproval among all R and I's. Close but no cigar. There are probably some that are closer, or perhaps even some that already do pass that threshold however I am only counting polls post the the creation of this question.