Hi Andrew, yes sir, the barrel is not threaded, this is Illinois legal.
budsgunshop.com/feeds/state_reg/illinois_restrictions.pdf ,
Stay safe & have a great day!

Hi Andrew and welcome. This model is 100% IL legal as configured. Cheers, stay safe and enjoy!

This model is good to go.
In Illinois, the legality of a Ruger 10/22 depends on its configuration. A standard, unmodified Ruger 10/22 is not considered an assault weapon and is legal to own. However, if it's modified with features that make it an assault weapon according to Illinois State Police, as defined by 720 ILCS 5/24-1.9 (a)(1), it can be restricted, according to the Illinois State Police . For example, a Ruger 10/22 with a pistol grip, a collapsible stock, and a large capacity magazine might be considered restricted.

budsgunshop.com/feeds/state_reg/illinois_restrictions.pdf