The COLLATE attribute of a column only affects the way how any indexes that are built on the column will be sorted. Thus, it should be possible to change the collation of a column without rebuilding the table, except if the column is part of the PRIMARY KEY.
Currently, changing the collation requires the table to be rebuilt with ALGORITHM=COPY, in all cases below:
(When testing versions predating
MDEV-13134, replace the ALGORITHM=INSTANT and ALGORITHM=NOCOPY with the broader clause ALGORITHM=INPLACE.)