Most flags are made of two regional indicator symbols, like this for the United Kingdom which has ISO 3166 code GB:
U+1F1EC REGIONAL INDICATOR SYMBOL LETTER G
U+1F1E7 REGIONAL INDICATOR SYMBOL LETTER B
If the font has flags, it should render this as a Union Jack, but if it doesn’t, it should render something along the lines of “GB” (which, frankly, is generally more useful if you try using flags without labels).
But Scotland has the ISO 3166 code GB-SCT, a format the regional indicators weren’t designed to cope with (for better or for worse), so it uses a different encoding technique and is comprised of the following sequence of seven scalar values:
U+1F3F4 WAVING BLACK FLAG
U+E0067 TAG LATIN SMALL LETTER G
U+E0062 TAG LATIN SMALL LETTER B
U+E0073 TAG LATIN SMALL LETTER S
U+E0063 TAG LATIN SMALL LETTER C
U+E0074 TAG LATIN SMALL LETTER T
U+E007F CANCEL TAG
As you observe, this has a significantly worse fallback behaviour: the tag characters are non-printing, so you get just a black flag.
Most flags are made of two regional indicator symbols, like this for the United Kingdom which has ISO 3166 code GB:
If the font has flags, it should render this as a Union Jack, but if it doesn’t, it should render something along the lines of “GB” (which, frankly, is generally more useful if you try using flags without labels).But Scotland has the ISO 3166 code GB-SCT, a format the regional indicators weren’t designed to cope with (for better or for worse), so it uses a different encoding technique and is comprised of the following sequence of seven scalar values:
As you observe, this has a significantly worse fallback behaviour: the tag characters are non-printing, so you get just a black flag.