Is it permissible to use dating apps for direct communication with a potential marriage partner, or must one have a Mahram present? And can one flirt slightly with a potential spouse?
Direct communication with potential spouse must remain within the frame of Shariah as both of you are still Non Mahram to each other. Flirting or flirtation with a potential spouse remains Haraam till both of you enter in an Islamic contract Aqd which allows that. Chatting should never contain any emotional content before having a valid Aqd between you. If both if you want to meet, it should be in the presence of another person to avoid the Khalwah (private meeting) which is not permissible with out a valid Aqd.
Wassalam.