ΔE 21.9, loose: different enough that you should pick on purpose. Smalt Hue is a little lighter, warmer than Lothern Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Smalt Hue is a little lighter, warmer than Lothern Blue.
The same difference applies the other way round: Lothern Blue is a little darker, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Lothern Blue on the colour wheel See Smalt Hue on the colour wheel
All matches: Lothern Blue equivalents · Smalt Hue equivalents