Why the contest/friction between Indigo/Indi or so it seems to me IMO - most Astro users couldn't care a fig what software they use as long as it works in the way they want to work.
IMHO and simple experience :-
for DSLR
1. Indi works well and is fairly mature ,as it uses Gphoto2 (as I guess Indigo does for Linux) ,but it cannot be used by any Windows Client (unless you know different).
2. Indigo has a RPI based Web image (Indigosky) that will connect a DSLR but does not have the functionality/robustness of Indi Ekos- Plus Indigo ,IMO, seems to be more concentrated on Apple kit. APT was released when I last tried Indigosky - Stage0 ?
3. APT,in Windows only, has the big advantage as it uses Canon's own SDK (Canon are a pain IMO) which is not available on Linux/Unix as far as I am aware and does not allow DSLR or native ZWO access on Indi or Indigo at this stage. Although this was released in Jan2019 which suggests Linux support
www.canon-europe.com/press-centre/press-...sdk-and-api-package/
IMHO (which doesn't count for much) APT have made a mistake in not including DSLR users in the initial release - but its their software and therefore their decision - good luck APT it is good software(I have used it for 4yrs) . Guess I am too focused on DSLR use but then there are many such users and they are not Apple based.
If I am wrong about what does work or doesn't etc - please correct me.