Tim commented with reference to the Pali commentarial explanation of sutta as suvutta:

But this is not really much to support sutta < sūkta, since the regular Pāli form parallel to sūkta includes the glide -v-, as Skt ukta ~ Pāli vutta and similarly in other MIA languages, which all seem to preserve the initial v- of the verbal root *vac- (Pischel §337), despite the vowel change a > u before a labial (§104).

But unless I am misreading something here, Pischel (§337) notes that Jaina Śaurasenī, Śaurasenī and Māgadhī all have utta < ukta

And Turner’s A comparative dictionary of the Indo-Aryan languages includes Prakrit sutta under sūkta:

13545 sūktá ʻ well recited ʼ RV., ʻ eloquent ʼ MatsyaP. [su -- 2, uktá -- ]
Pk. sutta -- ʻ handsomely said ʼ; OG. sūta ʻ speaking properly ʼ.

Rupert