Having a blind person automatically have better senses.
Having a gay person have issues with coming out, if they’re from a milieu where it’s not likely to impact their life much. I’ve seen a fair few things in the past few years where middle-class white people from non-religious backgrounds were hiding their relationships, and me and all my other middle-class gay friends were like huh? Tell them. It felt like the stories were being written by a person from a different generation. I’m 45 and grew up under section 28, but none of my family or wider friends gives a shit now.
Having a person from a Muslim background have problems with their family due to FGM, homosexuality, an uncle into terrorism (it’s always an uncle), etc. Those can be issues for some people, but most Muslims are just people worried about job retention and house prices and whether it’s the right weather to take a jacket out or not. And that includes most of the Muslims who are gay or have terrorist uncles.
Having a person with a disability be unmasked as faking it. In cop shows, it has got better, but all the same, if there’s a disability, it’s often a Chekov’s gun, there for a reason rather than just a feature, like them being from New Hampshire or liking opera.
Basically, don’t have those characteristics you’re thinking of - sex, race, nationality, disability - be Chekov’s guns.
Don’t shy away from mentioning those characteristics, though. They do build up a character. Never mentioning appearance at all would be weird and make it hard to tell people apart. Especially don’t shy away from mentioning if someone is non-white if you’ve stated or implied that other characters are white - “default white.” And people will notice if someone’s got a limp or a lazy eye, a turban or a kippah, same as they’ll notice if someone’s tall or short.
But just have it be part of their character, not the reason they’re in the story.
One tiny thing - for character names of foreign characters, maybe spend two minutes googling baby names for that area in the age they were born. I think there are more English TV characters called Nigel than have ever been born in England, and almost all of the real ones are over 60.