Gambia: Revolut works in Gambia at most popular ATMs incl Standard Chartered (not too many in the country anyway as of Apr 18). Note that all ATMs charge between 150-200 Dalasi (that’s £2-£3) for any foreign card use, this is per ATM transaction.
Senegal: Revolut worked in Senegal (Casamance region) at Societe Generale bank. No transaction charge levied by this ATM.
Guinea Bissau: Revolut DID NOT WORK at any of the ATMs I tried in the capital Bissau, including BAO (Banque Afrique Ocidental) and Ecobank which were the two common ones. Had to resort to using my Barclays UK debit card (Visa), which worked fine.