We could say
it was painted beautifully
to convey that the way it was painted was beautiful. "beautifully" being the adverbal form of beautiful (an adjective).
What if the adjective is "lovely": How would you convey that the way it was painted was lovely? Is it:
it was painted lovelyly
This sounds/feels weird and I have never heard/seen it used.
Furtherm "it was painted lovely" seems an error of grammar.
Is there a rule/guideline that adjectives ending in "ly" have no adverbal form and can't be used as adverbs? Or should we just use the adjectival form for the adverb even if it is grammatically incorrect?