This "FirstEver" guy is not a dev. He stole UnlegacyAndroid builds and tossed in free apps and tools such as Magisk that you can install yourself, and called it "his rom" all the while plastering donate buttons all over his website. He was banned from XDA for this behaviour but kept making new accounts to promote that stolen ROM. I'd recommend not supporting such people who have such blatant disregard for other people's hard work.
Well you're right. I didn't know that before. Anyway, I'm using another ROM now. Just wanna solve this BT issue.