MySQL 8: Truncate table stuck in `checking permissions` state for minutes
Hence my advice not to have more than about 50 partitions in a table.  Or to abandon partitioning altogether.

What may be happening:  table_open_cache (or one of the other caches) may be too small, and, hence, thrashing.

To verify that theory, I need to check several things.  Please provide SHOW GLOBAL STATUS;, SHOW VARIABLES; and how much RAM you have.  More details.

To critique the partitioning, please provide SHOW CREATE TABLE for at least one of the tables with a lot of partitions.

And you are TRUNCATEing a table with a lot of partitions?

If possible, look in the filesystem and list some of the files for that table.