is it a sin to participate in other denomination services?

I heard somewhere but cannot recall where, that it is a sin if a practicing Catholic participates in a non Catholic denomination service. Could you please clarify if this is true; to what extent this would apply, for example, if one is accompanying a friend to their church, attending a family event, or volunteering as an usher, to participating in their communion ceremony.
Thank you

I heard somewhere but cannot recall where, that it is a sin if a practicing Catholic participates in a non Catholic denomination service. Could you please clarify if this is true; to what extent this would apply, for example, if one is accompanying a friend to their church, attending a family event, or volunteering as an usher, to participating in their communion ceremony.
Thank you

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