Overriding hyphenation rules

[greleigh]

I believe this is more of an issue with documentation, though I found great confusion in the way babel handles/ignores overrides through \babelprovide.

Example in case. Main language should be UKenglish but with USenglish hyphenations (UKenglish hyphenation rules are for “Oxford” English and are far from common British English but that’s another matter).

Expected solution based on https://latex3.github.io/babel/guides/using-babelprovide-to-modify-or-extend-locales.html would be

\documentclass{minimal}
\usepackage[UKenglish]{babel}
\babelprovide[hyphenrules=USenglish]{UKenglish} % or
% \babelprovide[hyphenrules=english]{UKenglish} % or even
% \babelprovide[hyphenrules=USenglish,main]{UKenglish}
\showhyphens{versatile acknowledge} % gives ver-sat-ile ac-know-ledge

Working solution is to load babel with nil language and set UKenglish as main language:

\documentclass{minimal}
\usepackage{babel} % load `nil` language
\babelprovide[import,hyphenrules=USenglish,main]{UKenglish} % option `import` provides \today etc.
\showhyphens{versatile acknowledge} % gives ver-sa-tile ac-knowl-edge

I could find no comparable documentation in the babel.pdf (version 3.86) for setting hyphenation patterns.

[jbezos]

I think it’s related to https://github.com/latex3/babel/issues/122#issuecomment-800248692.