Oh yes, even if your self-built board works after the correct flashing of the bootloader and then the program, the capacitors I recommend are still important and indispensable, because in rough, daily use there are different conditions than in the electronics laboratory or on the crafting table. Especially when motors and the like are controlled with it. I am telling you this because I have a lot of experience in these things, I learned to build control systems and have been using electronics as a hobby for 45 years. I have also designed and built many boards with Atmega's and Attiny controllers. I just want to keep you from the effect 'But everything worked so well at home, why does it suddenly no longer work in the built-in state at the destination'. Because such errors are very difficult to find, because as soon as you move the board to another place, or even remove it sufficiently from a source of interference, they disappear and may not even be measurable for you. such - sometimes it works, sometimes it doesn't work - mistakes can drive you to despair.