GerdaOS looks really promising. I've always felt some disdain towards KaiOS for taking B2G and continuing its development and promotion as a closed-source fork with a heavily walled-off ecosystem, but GerdaOS seems to be the liberating force to help overcome the tyranny of the limits artificially imposed upon an open OS by the hand of capitalism. (Also, I love the name and the mythos behind it.)
Though apparently ADB access can be enabled within vanilla KaiOS as well, by entering
*#*#debug#*#*), via which it's also possible to gain root access or at least some privilege escalation. At least Kai didn't take everything out.