Hey everyone, we could start by mentioning some examples in each language and why it is considered an MRL language. I will start by mentioning some examples in Arabic .
Basically, the complexity of Arabic comes from the problem of non-concatenative morphology which happens when morphemes are not added in a linear fashion. I will mention to examples of concatenative and non-concatenative morphology


Concatenative morphology: Let us consider the verb يعلم (to know) in which we added the morpheme ي to the stem علم to represent the present tense . We can also construct plurals like يعلمون (they know) which adds prefixes: ي and suffixes ون to the same stem.

Non-concatenative morphology: happens mostly when the stem is modified/added to a template in a non-linear fashion. For example, broken or irregular plurals happens a lot in Arabic which adds the stem of the word into a template to create the plural. For instance, the word كاتب (writer) whereas the plural form is كتاب (writers).