"Passing away" is the Pali "vaya", as found in the Buddha's last words, as follows:
‘Conditions fall apart. Persist with diligence.’
vayadhammā saṅkhārā, appamādena sampādetha.
DN 16
It appears by the content of the Satipatthana Sutta the term "Dhamma" refers to various "teachings", "principles" or "truths" of the Buddha, such as the seven factors of enlightenment and the four noble truths.
SinceThus, monks such as Bhikkhus Buddhadasa & Sujato translate Dhamma here as Truths or Principles. However, is should noted the common illogical translation here of "dhamma" is "mental objects".
Regardless of the translations, since the development fruition of the seven factors of enlightenment and the realisation of the four noble truths are permanent in the mind of an Arahant, obviously these dhammas cannot be subject to passing away/destruction (vaya).
For example, MN 12 says about an Arahant's realisation:
Sariputta, even if you have to carry me about on a bed, still there will be no change in the lucidity of the Tathagata's wisdom.
SN 12.20 (about Dependent Origination) and AN 3.136 (about the Three Characteristics) say about the Dhammas an Arahant realises:
Whether Realized Ones arise or not, this law of nature persists, this regularity of natural principles, this invariance of natural principles.
Also, the term "arising" ("samudaya") is explained in SN 22.5 as when a monk "approves, welcomes and keeps clinging" to the aggregates. It follows, for one that has entered the Path, clinging to the seven factors of enlightenment and the realisation of the four noble truths is as equally ridiculous as these dhammas passing away.
These obvious points shows how questionable the Satipatthana Sutta is. Bhikkhu Sujato called the Satipatthana Sutta the "Piltdown Sutta". "Piltdown" was a term used in a certain scientific fraud. Yet my answer will probably receive lots of down votes by those who worship ink & paper and who worship the Burmese gurus who worship the (fraudulent) Satipatthana Suttas.