hey folks, more of a libPD question than PD per se... i'm using libPD with Unity for an upcoming iOS app i want to build and looking for good synth filter alternatives. i may want to put it on the App store so using anything with expr~ or fexpr~ is out, unfortunately.

As of about 2 years ago, expr and relatives are LGPL and thus compatible with the App Store. I’m not sure why that info keeps propagating, you must have read some old posts before we resolved that issue.

i recently ran into the [bob~] object which seems useful and is under BSD license but initial searches on how to compile externals in libPD have not been successful.

As of version libpd 0.8+, the built in extras (bob~, bonk~, etc) can be compiled into the c lib using EXTRA=true, see https://github.com/libpd/libpd#androidmk-makefile-libpdxcodeproj-libpd_winsln

ideally i'd love something i could just use in vanilla, as recompiling libPD for C# is kind of a chore for my skillset. anyone got an idea where i might find good vanilla resonant filters not using expr~/fexpr~ compatible with libPD?

Try rjlib: https://github.com/rjdj/rjlib