I don't think it's fair to expect third-party developers to keep track of all this and produce fully compliant packages without resorting to hacks like fpm. I have a couple of staging servers running Alpine and am thinking of switching more serious workloads to it. Maybe switching fully some day if that works out fine. I was surprised how easy it is to write Alpine packages, they don't change formats every week so your knowledge stays current, and I wrap even basic shell scripts in packages now. Not something I ever did for Debian systems.
Have a look at official packages for an example:
https://git.alpinelinux.org/aports/tree/main?h=3.12-stable
https://git.alpinelinux.org/aports/tree/community?h=3.12-sta...