A shortlist of six subs with each one's self-promotion policy written down.
Reddit is not one channel, it is several hundred with incompatible rules. The work is research, and it is worth doing properly once.
Use a site search on reddit.com with a competitor's name. The threads that come back tell you which subs actually talk about tools like yours.
They differ completely: outright ban, a ratio requirement, a designated day, or a required flair. The rule is in the sidebar and it is enforced.
Age and karma thresholds silently filter most new accounts. If you fail them, that sub is a month away, not today.
Six subs, each with policy, allowed format, best day and how strict the mods are. This becomes the plan for the next guide.