I think there is a lot of good advice here but in my opinion the number one thing to do based on what you have described is to eat a lot more. I feel like “eat more, train more” has never failed me personally. If you could choose between maintaining dietary habits and training less VS eating constantly and training more which would you choose? I love training and riding my bike hard so I choose the latter, personally.
If you haven’t looked at it, try checking where you are at in terms of energy availability :
I wouldn’t be surprised if you would want to be at around 2500 baseline calories PLUS exercise calories (bike, long walk), so maybe 3500+ per day depending on your exercise. I also wouldn’t be surprised if you initially gain 2-3 kilos and then immediately level off if you are training hard. You might need quite a bit more to gain significant weight.
I’m sure there are exceptions to this but in my mind, big adaptations (e.g. gaining 60 watts of threshold) require a surplus of energy. You have to do the work but also provide the raw material to adapt.
Finally, from the meals you have posted I would be wary of eating too “clean”. Salads and lean meats are great but your body needs fat too. I’m not saying junk food but you don’t seem to be vegetarian so eat some steak. Red meat will give you iron (you mentioned you are supplementing) and lots of building blocks for a strong body.