In the closing moments of the last episode of Star Trek: Picard, the show hinted that Seven of Nine was interested in a lesbian relationship with the other woman on the ship. But in the last episode of Voyager, it was stated that she had married Commander Chakotay. Is he dead or are they divorced or separated?
The present-day versions of Seven and Chakotay weren't married in the final episode of Voyager, "Endgame"; they were only dating at the time. It was revealed that they later married in the alternate future Admiral Janeway time-travelled back from, and that Seven died in that timeline.
ADMIRAL: Seven of Nine is going to die.
ADMIRAL: Three years from now. She'll be injured on an away mission. She'll make it back to Voyager, and die in the arms of her husband.
ADMIRAL: Chakotay. He'll never be the same after Seven's death, and neither will you.
However, since Admiral Janeway succeeded in her mission to alter history, that alternate future was erased from existence, and there's no indication I'm aware of that Seven and Chakotay actually got married in the revised and currently canon timeline.
As for what happened to their relationship, Seven's page on Memory Alpha states the following:
Michael Chabon stated on his Instagram that, considering the evidence, it was safe to assume Seven and Chakotay's relationship had come to an end by 2399. 
Chabon also stated in an interview with Queerty that Seven went on to "explore the spectrum of human relationships" in the years following the end of Voyager:
Same thing with Seven of Nine, having to catch up after such along absence from the human race. If you think about that, it almost seems unnatural that she wouldn’t’ have had partners of other genders. It seems clear she would have. So even if we didn’t see that on Voyager, years have passed. In that time, she’s continued to explore the spectrum of human relationships in a broader way. So in our show, there are echos and implications of that.
Regarding the point about Seven "switching sides", the fact that her first romantic relationship happened to be with a man doesn't mean she was strictly heterosexual to begin with. And the fact that she's more recently shown romantic/sexual interest in women doesn't mean she's now strictly homosexual.
Given that she's shown interest in men and women at different points in her life, it's more logical to conclude that she's bisexual, and likely always was, whether she was consciously aware of it or not.