Very simple. Not converted, not married.
By law in Indonesia a marriage must be done within the same faith.
Like you, before settling in Indonesia two decades ago, I thought that Catholic and Protestant didn't have much differences. Then I came to Manado. Situation here is probably how it was a couple of century ago or more in Europe, or at least in France where I am from. Catholic and Protestant are very well aware of their differences and are estranged cousins.
In my family we have Catholics and Protestants. Everything goes well until it comes to religious discussions or religious affairs. Then you can see that the two communities tolerate each others but don't mix more than necessary.
One of my cousin, a Catholic, was engaged to a young chap who happened to be a Protestant. Came the time to discuss marriage but no agreement got reached, both of the would-be spouse wanted to remain officially in their religion. They broke up and my cousin wrote on her FB account (in English) "Born Catholic, Raised Catholic, and Die Catholic". The whole Catholic branch of the family cheered up inundating her post of "like" while the Protestant branch of the family stayed away from the post, just bitching privately on how stupid she was and that she would die alone...etc
I may be the exception tolerated by the two side of the family. The Protestants are happy with my "conversion" despite the fact that I don't attend Church and the Catholics of my family consider me "one of them" in spite of my "conversion". As long as I don't turn Muslim, all is fine. Buddhist would be borderline but probably still OK since I have a strong social influence within the family.

If they knew I am atheist, quite a few would faint, or worse, for sure.
Don't underestimate the weight and influence of Religion in Indonesia. It's probably beyond anything you have experienced, and this in all faith.