But the basic difference would be that we would start off with discussions on our device, and then gradually discuss ways and means regarding how we can find out workable solutions if we had no GAFAM product.

To only leverage already built environments is no way to ensure healthy growth. So while in a hurry it could help, I'd advise and incentivize on building that on calmer times.

but l find the forums/communities great for discussion purposes

Other than XDA already mentioned by frongt, of which is pretty overarching already, there are plenty of public forums still floating around, and that you could also find a corner to discuss experiences with Android.

Forums such as from GBAtemp, Retropie, GOG, AtariAge, Fuwanovel, GameFAQS, etc. may have corners where these types of discussions are allowed, though I'd imagine usually on the general or off-topic sections since their purposes aren't about Android specifically. You could also crosspost your question to !Forums@sh.itjust.works so you could get more suggestions of places to check.

And if you'd wish to stick to the fediverse but wants a PHP/board forums-oriented discussion structure, might I suggest NodeBB? It's compatible with Lemmy's community structure. Though better look for the ones with ActivityPub integration, as it was added on a later update and so some sites may still not have it enabled (or decided not to).

Why can't you do that here?