Is it permissible to conduct a marriage contract (nikah) via the Internet using a video call, in the presence of a legitimate sheikh and witnesses from both parties, to ensure the continuity of the legitimate relationship and avoid forbidden acts, due to the inability to travel for two years?

Those who love each other must practice chastity and repent from what Allah has forbidden. Marriage is the solution. A marriage contract is not valid via the internet or phone. However, the guardian (wali) or the suitor can appoint someone to act on their behalf in the contract. The guardian and witnesses must be present at the contracting session. If marriage is not possible, then cut off the relationship and ask Allah for what is good.