How to force "re-TOAST" after changing STORAGE or COMPRESSION?

Hi. If I do either or both of the changes below:

ddevienne=> alter table dd alter column val set compression lz4;
ALTER TABLE
ddevienne=> alter table dd alter column val set storage extended;
ALTER TABLE

According to the doc, the table is NOT changed.
In my case, I DO want to have the bytea column rewritten
according to the new STORAGE and/or COMPRESSION.
The doc doesn't mention how to achieve that.

VACUUM?
VACUUM FULL?
Else?

Also, pre-v14, is eXtended STORAGE always compressed with pglz?
The reason I'm asking, is that I don't see much difference between
sum(length(bytea_col)) and pg_total_relation_size(reltoastrelid), thus
I'm not quite sure whether compression happens or not, in fact.

Note that most of the data is floating point arrays inside a bytea columns,
thus I guess unless one shuffles the bytes around, it doesn't compress too
well.

Thanks, --DD