Does anyone know of a source for the practice of not walking around indoors without shoes? (I am seeking an actual source, not speculation)
I lived for a while in a very strict Chassidic community. Walking around indoors without shoes was seen as an extremely serious offence, even when done with socks and stockings, and on a thick carpet.
The reason was that without shoes, one could be negatively affected by the ground's klipos.
Mesechta Shabbos 129a, Pesachim 112a. One should sell their property for shoes so not to walk barefoot.
Rashi in Shabbos states, there is nothing more disgraceful than walking barefoot.
RAMA 2:6 states this is the halacha, forbidden to walk barefoot.
100% forbidden to dress inappropriately in a shul which includes not wearing socks (even if you have shoes on), and other things like shorts, etc.
Mishna Berurah 2:14 says that if you are in an Arab country where it is normal not to wear shoes than it is permitted. Stressing here ARAB countries.
Maaseh Avrohom (circa 1860 or so) quotes the Chesed L'Avrohom (master of Kabalah in both ARIZAL and Cordovo, circa 1600 or so), states that shouldn't walk barefoot because there is a ruach raah (evil spirit) on the ground connected to the snake from the Gan Eden times. However this doesn't apply to Eretz Yisroel when it is ruled by Jews (I am not getting into if this is those times now....too controversial for me).
I hope I gave enough sources with my explanations to satisfy the needs. Have a great Shabbos