When using radattr together with multilink the generated filename is incorrect as ifname is not yet available. The patch at the referenced URL resolves this issue. Reproducible: Always
Created attachment 311045 [details, diff] ppp-radattr.patch patch from above URL, slightly modified in order to apply cleanly using patch -p1.
Please, send this patch to upstream developers here[1] [1] - https://github.com/paulusmack/ppp