So let me add to my previous answer. Seems like there are a few goals here so let's take them one at a time:
Getting better at playing in front of people, IE overcoming stage fright.
Open mics 'can' be good but a lot depends on finding the right sort of open mic. What I hate most is when, once people have played, they leave. If you are last on the list, you can end up playing to the bar staff. Been there, done that.
Retirement homes. They are often happy to have someone come in and play. I've just started doing this and it's a lot of fun. It's usually a captive audience (or almost) and you need about an hour of music, which is a lot when you are playing instrumentals unless you can really embellish pieces or do a lot of improv around a theme, but it's all good practice. Even a 30 minute stint is a start.
Meetup groups. When I played piano I joined a piano group where we'd get together once a month at someone's house and play one or two pieces. I am no great player and there were some concert level pianists there but everyone brings something to the table and the whole point of the group was to be supportive. I started a similar accordion group where I live (Near Raleigh NC) and we get together and play, same concept, It's all good practice and getting that next piece right for the next session gives you something to work towards.
Jam sessions. Depends on the type of music I guess but I've been to 'pop' music jam sessions (Copperhead road on an accordion is cool, especially the intro) and I currently attend an Irish session from time to time. The Irish session is interesting because it's all play by ear, not something I do not do well but again, taking part is half the battle, the rest comes with practice.
Farmer's markets are always looking for musicians to play. Often the 'list' of summer dates fills up pretty quickly but I play spring and fall and sometime the dead of winter, summer is too hot for me no matter what instrument I am playing! The advantage of playing 'out of season' is that if the weather looks nice for the market day (often Saturday mornings), you can often email as late as the day before and just ask if they would like you to play. Often the answer is yes. Once your foot is in the door at a market you can sometimes just turn up and offer to play but as I say, that only works in the colder months.
Coffee shops. I am lucky I guess but there's a coffee shop near me that is very supportive of local musicians and, until the covid rubbish hit, would actually pay folk like me (who really just play for fun) a decent rate for a couple of hours of low key/background/easy listening type music. Some coffee shops can be a little like bars (everyone lookingt at their phones) so again, it's a case of finding a venue that you are comfortable in
Probably not going to happen busking. Typical rate for me at a farmer's market is about $8 an hour.I have had a couple of $20/hours days but they are few and far between. Hardly earth shattering but the point is to have fun.
If you want to make real money, you are going to have to play bars and for that you need a good three hours of music minimum, and you'll probably need to sing so a PA for voice and probably mics for the accordion, unless you go electric so the bill, just to earn a few $ quickly builds unless you happen to have acquired most of it through other projects.
Finding somewhere to play.
Mostly already covered above but lets consider 'real' busking which I think of as simply playing in the street for tips.
You mention that where you want to play does not allow it but what 'exactly' do they not allow, and is it private property of city property?
One could always argue one's first amendment rights and the US supreme court has ruled that performing music is a form of protected speech under that amendment. However....
Do you really want to argue that with the cops? Personally I'd just move on when asked.
You can always ask the property owners if you could play there. There's a little French village type shopping plaza near me, lots of crafty shops and the like. I've played there a couple of times simply by emailing them and asking them if they'd like someone (me) to play some accordion music (accordion fits the French theme very well) just around the plaza. It's not costing them anything. A couple of samples of your playing does not hurt either so they know you don't totally suck (it is their business after all).
If nothing else towns usually have a noise ordinance. Any Harley riding by busts that every day but it's soon gone. I have always aimed to play so that you could walk by me (hopefully tipping on the way) but still hold a normal conversation.
Ordinances. The town near me (Raleigh) actually has a street performer's ordinance and requires a permit ($40/year. July to July) in order to play on the streets there although I am not sure that all the people I have seen playing (Sax usually which is NOT quiet) around the Arts center on a Saturday night have permits but I could be wrong. However, where I live does not have, that I can find anyway, a specific ordinance regarding street performers but there is one for pan handlers and the usual noise ordinance. Some places also have ordinances regarding amplification although I am not sure how the Roland accordions would fit into that although I think that since it's built in, and not that loud, you might get away with it.
As long as there is no ordinance specifically preventing it, you can always just go and play, be respectful to the businesses and people around you and if asked to move, just do so.
Worse case, contact city hall and ask them, maybe even table a question at an upcoming public meeting asking them to clarify the situation and possible even put forward an argument for allowing it if you could show that it would enhance the local 'vibe' which in turn increaes foot traffic which means more money for local businesses.
I sometimes (just did tonight) go down town, sit on a bench and just play. I do not have a tip jar or anything suggesting that I am soliciting payment and in fact I tell people that when (and they do) put money in my accordion bag. But again, not getting rich doing this. I might get a coffee out of it. People watching is far more fun. Some will engage me, stop, talk, others just smile as they walk by and some just plain ignore me (a 6' 5" 250 lb guy playing an accordion is hard to ignore but some manage it!). All part of the fun to me.
I think a lot depends on where you are in a town. If you are in front of a shop and the shop staff think you are possibly putting people off from entering the shop, I can see they might call the cops on you. Same if your repertoire is only four tunes and you play the same stuff endlessly, think those bucket drummers, cool to see/hear for about 5 minutes, but all day, I think not!
Anyway, as Forest Gump would say That's all I've got to say on the matter"...