A non Jewish family member asks for some paper and matches from you so they can do a “solstice ritual” (which likely includes prayers to Mother Earth and the like). Are you allowed to give them the paper and matches?
The Gemara is clear that lifnei iveir applies to a non-Jew regarding his sheva mitzvot, of which avodah zarah is on the top of the list (Avodah Zarah 6a). However, that is limited to תרי עברי דנהר – when the non-Jew cannot get it himself. However, if he has access to it – חד עכרה דנהר – it is not לפני עוור on the Biblical level. Is it a Rabbinic problem? Tosafot and the Rishonim say – to give a davar assur to Jew, for whom we have an ערבות responsibility, חד עברא דנהר is a problem, to give it to a non-Jew it is not. See (among others) Tosafot Shabbat 3a, s.v. bava):
ואפילו מיירי שהיה יכול ליטלו אפילו לא היה בידו דלא עבר משום לפני עור דמושיט כוס יין לנזיר מוקי לה בפ”ק דמס’ עבודת כוכבים (דף ו:) דקאי בתרי עברי דנהרא מ”מ איסור דרבנן מיהא איכא שחייב להפרישו מאיסור ואפילו אי מיירי בנכרי דלא שייך לפני עור
Based on that distinction, the Jewish practice in the Middle Ages to sell religious objects to Christians was defended on the basis that the non-Jews could buy them elsewhere (although that was a debatable argument since: (a) they still had to be purchased, so the non-Jew did not have immediate access to them and (b) often the other person they could buy them from was also a Jew!). This also partly relied on the principle that non-Jews are not real עובדי עבודה זרה nowadays, but the חד עברא דנהרא was seen as a sufficient justification – Rema on YD 151:1,
י”א הא דאסור למכור להם דברים השייכים לעבודתם, היינו דוקא אם אין להם אחרים כיוצא בו או שלא יוכלו לקנות במקום אחר, אבל אם יכולים לקנות במקום אחר, מותר למכור להם כל דבר. (מרדכי דפ”ק דע”ז). ויש מחמירין. ונהגו להקל כסברא הראשונה, וכל בעל נפש יחמיר לעצמו.
So – since it is trivial to get paper and matches for oneself, this really is totally fine – much better than the need to buy a specialty item only sold in a few stores.
That being said, I find sometimes it is easier to speak about discomfort than about Halakha – “I’m happy to show you where they are, but I feel uncomfortable handing them to you, since this is such a non-Jewish form of religious worship.” If that won’t fly, then yes, it is fine to hand them the paper and matches.
What about alerting a non-Jew to the existence of a readily accessible resource? Thinking specifically about YouTube recordings of a Buddhist end of life/post death chant. Family members often don’t think to ask but experience significant comfort when offered.
We’d first have to know if that is really a type of avodah zarah practice/ worship or just a comforting chant. Like is saying המלאך הגואל אותי a Jewish religious practice directed towards God? I think not.
If it is some form of religious ritual or worship, then I think pointing them in that direction when they would not have done it anyways should definitely be considered at least as bad as a case of תרי עברי – they would not have done it without you, and here you are the one initiating it.