The only think that gives space back to the OS is shrinking the tablespace, so my general rule of thumb if I need to get space back to the OS is to move objects to a new tablespace. There's a couple of options to explore

Option 1 - complete move

- You could literally do an "alter table move online" and "alter index rebuild online" where appropriate grab every single table/index from tablespace "A" to move it to tablespace "B", where tablespace "B" is define will a small datafile set to autoextend.
- At the end of the exercise, tablespace "B" will be just big enough to hold the data and tablespace "A" is now empty and can be dropped

Option 2 - selective move

- Sometimes a tablespace is large only because there are a few tables/indexes up near the high watermark of the datafile(s), and there might be some large holes in the existing tablespace. In this instance,
its a waste of time/effort to move everything.
- So you would do something

select * from dba_extents order by file_id, block_id desc

to see if you only need to move a few segments about to free up a large chunk of datafile space out near the hwm.

In 23ai, this all gets much easier with a native shrink tablespace command.