Please help us help you and fill where relevant:
Your LimeSurvey version: 6.5.15+240701
Own server or LimeSurvey hosting: Own
Survey theme/template: Fruity
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Hello everyone, I'd like to ask about radioToStarRating plugin ( github.com/SondagesPro/LS-radioToStarRating ).
I've seen this post  forums.limesurvey.org/forum/can-i-do-thi...07180-array-of-stars that you can change radio button to star using the radioToStarRating plugin. But it's not compatible with Limesurvey Version 6.5.15+240701.

Are there any other alternative that similar to this plugin?

There is a good chance that it works if you open the config file and add LS 6 to the list of compatible versions. Have a look how the other versions are added and add LS 6 in a similar way and then test. I think there is a very good chance that it works.