ICU Specifies different LDML Collation Settings. Some of them seem pretty interesting, especially the ones on case and accent,

“Ignore accents”: strength=primary

“Ignore accents” but take case into account: strength=primary caseLevel=on

“Ignore case”: strength=secondary

“Ignore punctuation” (completely): strength=tertiary alternate=shifted

“Ignore punctuation” but distinguish among punctuation marks: strength=quaternary alternate=shifted potentially a better method of doing what

You can also see these documented here. Are these ICU options and settings possible with PostgreSQL 10 ICU collation support?

CREATE COLLATION special (provider = icu, locale = 'en@strength=primary'); SELECT 'Å' LIKE 'A' COLLATE "special"; # returns false

I've also tried the CLDR BCP47

Starting with ICU 54, collation attributes can be specified via locale keywords as well, in the old locale extension syntax (" el@colCaseFirst=upper ") or in language tag syntax ("el-u-kf-upper"). Keywords and values are case-insensitive. See the LDML Collation spec, Collation Settings, and the data file listing the valid collation keywords and their values. (The deprecated attributes kh/colHiraganaQuaternary and vt/variableTop are not supported.)

For that, this looked right

CREATE COLLATION special (provider = icu, locale = 'en-ks-level1'); SELECT 'Å' LIKE 'A' COLLATE "special"; # returns false

Also tried en-u-ks-level1 That method seems to be what the docs go for,