I looked around and found nothing to suggest "things" refer to objects.
NLT
30 They are backstabbers, haters of God, insolent, proud, and boastful.
They invent new ways of sinning, and they disobey their parents.
NIV
30 slanderers, God-haters, insolent, arrogant and boastful;
they invent ways of doing evil; they disobey their parents;
ESV
inventors of evil
BSB
They invent new forms of evil
NASB
inventors of evil,
AMP
inventors [of new forms] of evil
https://www.biblestudytools.com/dictionary/evil-thing/
An evil thing or evil things may be the thoughts of evil men, their plans or their deeds; or the things men suffer for their own wrongs; or the evils consequent upon the errors of others.
https://www.trinitycda.org/they-are-inventors-of-evil-things/
Louw-Nida’s Greek-English lexicon describes the phrase as follows – an inventor of evil things is “one who thinks up schemes or plans of action—‘contriver, inventor, one who thinks up.’ ἐφευρετὰς κακῶν ‘they think up ways of doing evil.” They scheme and plot and determine how to do evil.
https://biblehub.com/commentaries/romans/1-30.htm
Inventors of evil things - This doubtless refers to their seeking to find out new arts or plans to practice evil; new devices to gratify their lusts and passions.