The best advice that comes to mind is setting goals or rewarding yourself. Its easy to get distracted or lose focus when you have little motivation, or what needs to get done is not considered as interesting to your brain, so in order to get interested you can set goals and reward yourself. I found that rewarding myself along the way gives me reasons to stay focused. Hope this helps

Since I was in first grade I would use small snacks as rewards for completing small tasks! Finished a math problem? Snack! Remembered to start the dryer? Snack! Put your keys where they’re supposed to go? Snack! I’ve found that over time I start to build habits and rewire my reward system and I’m able to do bigger tasks while staying focused! Eventually this will lead to having a solid routine that you can do every day! Did I train myself like a dog? Yes, did it work? Somehow yes haha!

For stuff like cleaning a good way I've found to get my brain to focus on shit is to make up a cleaning character. Like to create a character who's doing the task you're doing and a reason for why they're doing it. My favorite character I put on is an overworked housewife who's planning on poisoning her family- I usually use that one to cook or do dishes

I was diagnosed with ADHD about 5 years ago and it’s still a daily struggle to get things done. Especially if I’m off of my medication. What I do is write down everything I have to do for the day and schedule out times to do it. That way although my mind does wander it can center me a little more, that way I can focus on what’s in front of me. I also have struggled with finding a place to do my work. For me the best place to do it is where there is no one and virtually no noise that way I don’t have anything taking my mind off of what needs to be done. I normally take frequent breaks if my mind starts wandering that way I don’t waste time trying to study or complete something when I can’t actually focus on and won’t remember what I am doing. What have you tried in the past to help you with this?

Meditation! It's basically mind exercise lol. You could try to get on meds but even if you do that (and in a timely manner) meditation will 100% help. You can find some resources for meditation, specifically ADHD meditation, very fast online. Good luck!