PHOEBE 2.2 introduces the capability to interpolate limb-darkening coefficients for a given ld_func (i.e. linear, quadratic, etc). In order to do so, there is now a new parameter called ld_mode which defaults to 'interp' and ld_mode_bol for bolometric limb-darkening used for irradiation/reflection which defaults to 'lookup' . ld_mode of 'interp' is the same behavior as ld_func='interp' in previous version of PHOEBE. Any code setting ld_func to 'interp' should now be changed to set ld_mode instead.
As ld_mode is set to 'interp' by default, the ld_func parameter is no longer visible. If setting ld_func to something other than 'interp', you must first change the value of ld_mode (to either 'manual' which allows setting ld_coeffs as in previous releases, or to 'lookup' which is the new behavior introduced in 2.2).
Similarly, as ld_mode_bol is set to 'lookup' by default, the ld_coeffs_bol parameters are no longer visible. If setting the coefficients, you must first change the value of ld_mode_bol to 'manual'.
For a more thorough explanation of the new behavior, see the updated limb darkening tutorial.