I hope at least the Unicode Consortium pulls their head out of their ass by then and defines sequences like

U+1F3F3 WAVING WHITE FLAG  
U+ FE0F VARIATION SELECTOR-16  
U+ 200D ZERO-WIDTH JOINER  
U+1F7E5 LARGE RED SQUARE  
U+ 200D ZERO-WIDTH JOINER  
U+1F7F7 (not yet existing) LARGE LIGHT ORANGE SQUARE  
U+ 200D ZERO-WIDTH JOINER  
U+ 21BC WHITE LARGE SQUARE  
U+ FE0F VARIATION SELECTOR-16 (forces emoji rendition of this pre-emoji character, also used in the existing trans flag sequence)  
U+ 200D ZERO-WIDTH JOINER  
U+1F7FA (not yet existing) LARGE LIGHT PURPLE SQUARE  
U+ 200D ZERO-WIDTH JOINER  
U+1F7EA LARGE PURPLE SQUARE

This would render as a striped flag like if supported on the platform (on devices before Unicode 20.0 like yours right now, the fallback is “🏳️‍🟥‍🟷‍⬜️‍🟺‍🟪”, much like the fallback of 🏳️‍⚧️ is “🏳️⚧️”). Fonts could include most common pride flags (with exact “canonical” color values) and/or the platforms could generate the stripes on the fly up to a limit. I think both approaches have been implemented for the family emoji set on some platforms (yup, those also use separate codepoints for members and ZWJs), after all. (I hope platforms adopt the latter approach, even though it enables arbitrary, evil “pride” flags like TERF or MAP − well, Unicode has always been able to express evil, valid Unicode sequences include U+0FD5 RIGHT-FACING SVASTI SIGN, U+1FAC3 PREGNANT MAN, U+20E0 COMBINING ENCLOSING CIRCLE BACKSLASH or the entire text of Mein Kampf.) And would people abuse it for color bitmap text art? Yes, like they do Braille now.