Muskwalker

Man, I miss furry cons.

Your suggestion is very regional specific and perhaps limited to the USA

(probably fine for OP, who indicated they live in the USA, but)

In many countries, like whole Europe, its literally impossible to get a “burner number” because any SIM card requires by law a personal verification

'Burner' in this context means 'cheap enough to be disposable', not necessarily 'anonymous'. It's not about being untraceable, it's just about not pinging all the Normal People who may know your main phone number with whatever difficult-to-explain profile info/icon you want to use.

Interesting to know about Europe though. I wouldn't expect to need a SIM card at all to get a phone number where I live. (I think that's a mobile phone thing; I've never owned one. Here I have my public/private phone numbers through online services like Textfree and Google Voice.)

Agree with the suggestion to get a burner number. The big one to be aware of is that Telegram users who have you in their phone contacts may get a notification that you've joined Telegram, so if you're using a number other people know then you'll want to make sure your profile is something you're fine with them seeing.

The 'local' timeline is probably more useful on niche servers.
Might also flavor your federated feed and make finding others in the niche more likely.
Also if the niche is of an unpopular or marginalized or nsfw sort, you'll know the local moderation will be more amenable to what you want to post about.

But in general it doesn't super matter, no.