Don't often post but as a former Stay at Home Dad and now with a wife who is a Stay at Home Mom I can offer some non-cringe advice:
1) Be ready to lean into adult interaction after your kid(s) go to bed. This means listening and communicating about the minutiae of the day with the toddler- eating, diaper changes, nap cycle, play time, stories, sickness. The days and weeks are long but the months and years go by quickly.
2) Stay at home parenting moods can be cyclical. It's fairly awesome to be able to take your child to the park, playground, push in a jogging stroller, going to the zoo when it's nice out in the spring/summer/fall. Winter time can be abysmal especially if you're moderately risk averse to covid.
3) Time to get lean on finances if you were budgeting her salary in your finances.
4) I agree with the poster that a Stay at Home Mom wants to have more sex. Enjoy it.
5) Find time to treat her and take the lead . I don't necessarily agree with the people who say women want to escape to do their own thing when you're home from work. They want you to be a part of raising the child when you are home. Take initiative to plan activities on your off days/evenings/mornings. You definitely have fewer chips to spend time with your friends or do individual activities when she's staying at home.
6) They forget what full time work is like. They become completely immersed in parenting and relate to the stresses/rigors of work less. You have to overcommunicate what you experience in the workplace or risk drifting apart. I'm not one to overshare work doldrums but you better get used to it.