Dear all,
I was facing the same issue with variables in mobile prototypes. The variables are working fine on desktop, chrome or safari but not working on figma mobile app or mobile browsers.
I found out that it is caused by custom fonts that I used. The fonts are not available on mobile so It crashes. When I set the fonts to Inter, It is working fine.
I saw that many people are struggling with this issue. I solved my problem by changing to default fonts, If you are facing the similar issue, try checking if you are using a font that is available on mobile phones.