Difference between seek and seek for?

And what is the difference between seek and seek for?

Seek means look for both in the literal sense: The police are seeking information … and in the figurative sense: Religions are always seeking the truth about life and death. Seek for is not used very often - in fact I would never use it and would prefer search for.

How to explain this sentence “Yet a great many processes depending on such research are sought for with complete secrecy until the stage at which patents can be taken out.”

Does it help to replace ‘are sought for’ with one of these, Xupeng?

are looked for
are searched out

Again, do ‘search for’ and ‘search out’ mean the same in this context?

‘Search out’ suggests a more determined approach than ‘search for’.

Thanks, Alan.