Hi OP, firstly, I think it's great that you're looking to make positive changes in this way (rather than more "faddy" diets) but agree with a recent PP that you've had some conflicting advice! Here is my two-pence worth.....
I listened to Chris and Xand van Tulleken's podcast about UPF (link below) and found it really enlightening. Part of the issue is that UPF is designed to be really addictive so that we eat more of it and therefore manufacturers sell more of their product.
An experiment was done where two groups of people were allowed to eat as much food as they wanted over a period of a few weeks. The food offered was identical in terms of calories, fat, protein etc but the only difference was that one group had this in the form of ultra-processed foods and the other group had non-UPF. The UPF group ate a lot more and gained significant weight compared to the other group (see podcast for all the finer details). The UPF does not trigger our satiety ("fullness") signals in the way normal food does.
So it is really difficult for us NOT to overeat if most of our diet is UPF. This must not be confused with processed food. A lot of food is classed as "processed" but is not bad for us in the specific way that UPF is.
So I agree with your plan to avoid UPF bread and either make it yourself, buy Jason's sourdough or buy proper bakery sourdough (a lot of pre-packaged sourdough in supermarkets is confusingly still UPF, but not Jason's). We make bread in a breadmaker now at home - so easy.
Definitely eat as wide a variety of plant-based foods as you can. All calories are not equal so eating (e.g.) 200 calories-worth of broccoli will keep you feeling full for a lot longer than 200 calories-worth of shop-bought UPF bread.
Plant-based foods include fruit, veg, beans, legumes, herbs, spices, nuts and seeds. The more different ones you eat, the healthier your gut bacteria and the less you crave UPF in the long run.
Some PPs have been advising you that you will overeat on healthy foods and have given advice to count calories/join Slimming World but that (well meaning) advice is so out of date!
You are absolutely on the right track here and more likely to be successful with long term weight loss if you cut out as much addictive UPF as possible. Don't worry about trying to restrict genuinely healthy food. Good luck with it all!
The only breakfasts we now have on offer at home are: porridge (with added frozen berries and mixed seeds), Weetabix, Shredded Wheat or toast (homemade bread) with butter/peanut butter and jam. We only get non-UPF peanut butter and Bonne Maman jam (no artificial sweeteners). So you can see how there is so much to consider! Artificial sweeteners are a whole topic in themselves but basically are worse than sugar!
In addition to the van Tullekens, I also recommend listening to the Zoe podcasts on Spotify - more evidence-based diet advice (although I wouldn't personally bother with the testing of blood sugar).
https://www.bbc.co.uk/sounds/brand/m0017tcz?partner=uk.co.bbc&origin=share-mobile