Superconductivity emerging from an electronic phase separation in the charge ordered phase of RbFe${}_2$As${}_2$

${}^{75}$As, ${}^{87}$Rb and ${}^{85}$Rb nuclear quadrupole resonance (NQR) and ${}^{87}$Rb nuclear magnetic resonance (NMR) measurements in RbFe${}_2$As${}_2$ iron-based superconductor are presented. We observe a marked broadening of ${}^{75}$As NQR spectrum below $T_0\simeq 140$ K which is associated with the onset of a charge order in the FeAs planes. Below $T_0$ we observe a power-law decrease in ${}^{75}$As nuclear spin-lattice relaxation rate down to $T^*\simeq 20$ K. Below that temperature the nuclei start to probe different dynamics owing to the different local electronic configurations induced by the charge order. A fraction of the nuclei probes spin dynamics associated with electrons approaching a localization while another fraction probes activated dynamics possibly associated with a pseudogap. These different trends are discussed in the light of an orbital selective behaviour expected for the electronic correlations.