In file backzone there is an entry for Africa/Lubumbashi
# Democratic Republic of the Congo (east)
Zone Africa/Lubumbashi  1:49:52 -       LMT     1897 Nov 9
                        2:00    -       CAT

There are scarce sources for time zones of former Belgian Congo.

My main source for its time zone history is
Henri le Corre, Régimes horaires pour l'Europe et l'Afrique.

He has for the eastern provinces of Zaire

GMT + 1 between 1897 Nov 9

GMT + 2 since 1920 Apr 25.

Shanks follows le Corre. As does Francoise Schneider Gauquelin in he book
Problèmes de l'heure resolus pout le monde entier.

I think this is sufficient reason to change the zone into

Zone Africa/Lubumbashi  1:49:52 -       LMT     1897 Nov 9
                        1:00    -       WAT     1920 Apr 25
                        2:00    -       CAT

For the province of Kisangani, formerly Stanleyville, le Corre gives a transition from GMT +1 to GMT + 2
on 1935 Jun 14. But as this agrees with Lubumbashi after 1970, I do not expect the creation of another
backzone entry for that. This task will be left for my private pre-1970 TZ extensions.