Mitsuboshi Colors and Do It Yourself!!, I want to say. These are both pretty short (12 episodes-ish), but I'm being cautious about what is meant by lighthearted/feelgood and trying to avoid anything with even trace amounts of Anime Bullshit in it. Depending on your tolerance levels I could recommend a buuuunch more things, since cute/fluffy anime has basically been my niche ever since I got into anime. Some good keywords to learn are iyashikei (healing-type anime) and CGDCT (Cute Girls Doing Cute Things).
Anyways, Mitsuboshi Colors (2018) is about these three little girls who call themselves "the Colors" and pretend to be heroes defending the peace in their little slice of Tokyo (which is really just an excuse for them to play games, goof off, and explore). They have a pet cat called Colonel Monochrome and get into frequent spats with the neighborhood cop Saitou. If you end up liking Mitsuboshi Colors, consider trying Hitoribocchi no Marumaruseikatsu (2019), about a socially anxious middle school girl trying to befriend her whole class. It's an adaptation of another manga by the same author as Mitsuboshi Colors, and is also pretty lighthearted/feelgood, just with some extremely trace amount of Anime Bullshit and a bit more crying.
Do It Yourself!! (2022) is basically about these girls at two neighboring high schools who start a DIY club in a disused shed together, and it's really sweet to see them working together to do all their projects, how characters who might not have cared for DIY at first gradually get into it, how it brings different kinds of people together and all that. It has a nice depiction of elderly people being active and helping the younger characters out, too, that you don't see very much of in anime, if anywhere. And if you liked Do It Yourself!!, consider checking out Keep Your Hands Off Eizouken! (2020), which is about three high school girls making an animated short film together. I think it has a similar vibe to Do It Yourself!!, but is maybe a bit more conflict-driven.