I had this exact issue earlier in the year - I wanted to increase my protein and fibre but also lose a few pounds.
I found taking an additive approach - trying to add protein and fibre to my existing diet - didn't work at all. It just stacked up calories.
I found a substitute approach - swapping out low protein or fibre foods for ones with higher content - worked better.
But I found a full mindset shift about the 'value' of food worked best, and actually made me really excited about new foods.
I started with a list of high protein and high fibre foods with calorie and portion information too.
Then I started from scratch with each meal and snack, sticking to calorie limits for each meal and snack, and getting as close to protein and fibre recommendations for each day. It helped me cut out a lot of empty shit. So I was approaching each meal thinking about its "value" - like am I getting the most out of every food stuff, every calorie here?
I've tweaked and experimented since the new year. But I'm on a really good vibe. So, for me, a tip would be to start from scratch with meal planning, and use AI to identify really high fibre food stuffs.
AI put me on to psyllium husk which has incredible amounts of fibre - 3g of husk gives about 7g of fibre.
It takes like tree bark that's been eaten and shat out, and then marinaded in arsehole sweat. But it's got lots of fibre.
If you stir it into some lemon flavoured drink (lemon squash, lemonade) and gobble it down quickly, its bearable.