SQL Server 2016

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create table test (col varchar(1000))
insert into test values
  ('Alecta PensionsfÃ¶rsÃ¤kring, Ã¶msesidigt')
, ('AelefÃ³nica, S.A.')
, ('Áæâàéêèěęėëöű')
3 rows affected

CREATE FUNCTION Utf8ToUcs(@src varchar(MAX)) 
RETURNS NVARCHAR(MAX) 
WITH SCHEMABINDING
AS
BEGIN
    DECLARE @i INT
          , @res NVARCHAR(MAX)=@src
          , @pi VARCHAR(18);
          
    SELECT 
      @pi = '%[à-ï][€-¿][€-¿]%'
    , @i = PATINDEX(@pi, @src COLLATE Latin1_General_BIN);
 
    WHILE @i > 0 
      SELECT 
        @res = STUFF(@res,@i,3, NCHAR(
                      ((ASCII(SUBSTRING(@src,@i,1))&31)*4096)
                     +((ASCII(SUBSTRING(@src,@i+1,1))&63)*64)
                     +(ASCII(SUBSTRING(@src,@i+2,1))&63)))
      , @src = STUFF(@src,@i,3,'.')
      , @i = PATINDEX(@pi,@src COLLATE Latin1_General_BIN);

    SELECT 
      @pi = '%[Â-ß][€-¿]%'
    , @i = PATINDEX(@pi,@src COLLATE Latin1_General_BIN);

    WHILE @i > 0 
      SELECT 
        @res = STUFF(@res,@i,2,NCHAR(
                       ((ASCII(SUBSTRING(@src,@i,1))&31)*64)
                       +(ASCII(SUBSTRING(@src,@i+1,1))&63)))
      , @src = STUFF(@src,@i,2,'.')
      , @i = PATINDEX(@pi,@src COLLATE Latin1_General_BIN);

    RETURN @res;
END;
select col
, dbo.Utf8ToUcs(col) as col_ucs
from test


col
col_ucs


Alecta PensionsfÃ¶rsÃ¤kring, Ã¶msesidigt
Alecta Pensionsförsäkring, ömsesidigt

AelefÃ³nica, S.A.
Aelefónica, S.A.

Áæâàéêèeeeëöu
Áæâàéêèeeeëöu


select col
, cast(dbo.Utf8ToUcs(col) as varchar(100)) Collate SQL_Latin1_General_CP1253_CI_AI as col_cp1253
from test


col
col_cp1253


Alecta PensionsfÃ¶rsÃ¤kring, Ã¶msesidigt
Alecta Pensionsforsakring, omsesidigt

AelefÃ³nica, S.A.
Aelefonica, S.A.

Áæâàéêèeeeëöu
A?aaeeeeeeeou

col	col_ucs
Alecta PensionsfÃ¶rsÃ¤kring, Ã¶msesidigt	Alecta Pensionsförsäkring, ömsesidigt
AelefÃ³nica, S.A.	Aelefónica, S.A.
Áæâàéêèeeeëöu	Áæâàéêèeeeëöu

col	col_cp1253
Alecta PensionsfÃ¶rsÃ¤kring, Ã¶msesidigt	Alecta Pensionsforsakring, omsesidigt
AelefÃ³nica, S.A.	Aelefonica, S.A.
Áæâàéêèeeeëöu	A?aaeeeeeeeou