Currently I only get rectangular boxes when I type (for example) 1FA60 Alt-X. The symbols show up in Insert Special Characters (under Xiangqi) but selecting this way for every use, every time is tiresome.
The current font doesn’t contain the glyph hence the rectangle. U+1FA60 is in the Supplementary Multilingual Plane. Not all fonts (I’d say the majority of them) contain SMP glyphs. The Special Characters dialog is special in that it automatically substitute fonts to show glyphs instead of rectangles.
For better answer, edit your question to mention OS name, LO version and font used in your text.
The solution may need to create a dedicated paragraph style and/or a companion character style.