The gr-iio blocks that are currently on github seem only to work with GnuRadio 3.7.x. I attempted to build against GnuRadio 3.8 and there are at least some header files changed in the local/include/gnuradio/analog directory such as sig_source_f.h etc. I have successfully built gr-iio from source for GnuRadio 18.104.22.168.
Has gr-iio been ported to GnuRadio 3.8 yet? Are there sources available?