Tested on today's master branch.

# radiusd -X
[...]
/etc/raddb/mods-enabled/mschap[11]: Failed to link to module 'rlm_mschap': /usr/lib/rlm_mschap.so: cannot open shared object file: No such file or directory

After removing /etc/raddb/mods-enabled/mschap:

# radiusd -X
[...]
/etc/raddb/mods-enabled/realm[21]: Failed to link to module 'rlm_realm': /usr/lib/rlm_realm.so: cannot open shared object file: No such file or directory

After removing /etc/raddb/mods-enabled/realm, something fails that I shouldn't remove:

# radiusd -X
[...]
/etc/raddb/mods-enabled/ntlm_auth[17]: ...t-key --domain=MYDOMAIN --username=%{mschap:User-Name} --password=%{User-Password}
/etc/raddb/mods-enabled/ntlm_auth[17]:                                         ^ Unknown module

Upon investigating package/freeradius-server/freeradius-server.mk, I've seen that the rlm_mschap and rlm_realm modules are explicitly disabled because "we don't have the dependencies" for them. I have removed these two lines which disable these modules. The package compiled fine and the server started working.

I don't know what was meant by not having the dependencies for these modules so I'm submitting a bug here to let someone with more experience in this project know.