Unicode symbol 266D (♭) will not appear in Scribus, whatever the font. Besides, I've made sure already that the symbol I want is contained in the font I am using, here
Times New Roman (Regular). The symbol does appear in the Story Editor (Ctrl+T), though. In the actual document, however, it is replaced with a weirdly positioned empty square, as can be seen on the screenshot below. As already mentioned, the problem persists with whatever the font. It also persists regardless of whether the text is placed within a text frame or within a table cell, as is the case in my screenshot.

In case it matters, here's a bit of information on what I'm trying to achieve: I'm trying to make a flashcard set, and will probably be redoing this in the future, so I want to find a way to not have to bother dragging the image of a flat, sharp or natural sign every time I want it to appear on a flashcard.
I'm using Scribus version 1.5.6.1, which was installed using the APT package manager on Debian GNU/Linux 11 (Bullseye), amd64.
P.S. In case you Google it and find an identical question on Super User, yes, that was me too. The reason I'm asking here also is that I need those flashcards as soon as I can. Wherever I get an answer first, I will link to that answer in whatever forum and credit the author.