I think there's a few groups on the deltarune subreddit who've checked out the system before, but I'm honestly not too sure! I've not heard a ton since putting it out, mostly just due to being busy and also not being sure where people'd even start something like that up xwx
AH- I work on projects like this solo, and the Heartbreaker content is mostly optional for play as opposed to required or necessary. I work a dayjob that eats up a lot of my spare time, and both Heartbreaker and the core Dialtone books took about a year each to fully flesh out, format, and create art for- all atop my other responsibilities such as taking care of friends and my partner, and the webcomic I put the majority of my time into. It's a lot of labor, and at present I don't make very much money for my artwork that'd let me do it full time, even though I'd really like to-charging for the optional content/artwork in Heartbreaker helps me get there a bit! 'w'b