What is the adverb form of discuss?

There isn't a direct adverb form of "discuss". You would use other adverbs to describe how something is discussed, for example:

* Thoroughly: They discussed the problem thoroughly.

* Briefly: We briefly discussed the options.

* Frankly: They discussed the matter frankly.

* Openly: The team openly discussed their concerns.

You can also use phrases like "in detail" or "at length" to describe how something is discussed.