According to
It seems to be the intended behavior that the # sign in the formatter URL is escaped.
However, for example
https://portal.mardi4nfdi.de/wiki/Item:Q10730
intends to link to 1.1#p2.t1.r4 but is then redirected to
https://dlmf.nist.gov/1.1%23p2.t1.r4
Maybe there is a simple trick to bypass this escaping.