I am able to use Reddit with VPN and email alias.
Reddit shadowban system is complex, I read a thread on it once with all the actions that might influence your internal scoring when your threshold is being passed for assumed bot activity, which puts the shadowban flag on you. Appealing it is often a waste of time.
My strategy is, use the same country for your VPN for the same account, do not post on big subreddits with a new account, they are more likely to restrict your comment anyway - which leads to your comment not generating any karma. You should start on smaller subreddits.
Do not spam comments. Even two comments in a few hours is almost too much for first days. It needs to be natural.
Under no circumstances delete a comment, even if it has been restricted by a subreddit. Deleting a comment points to bot activity, and makes you shadowflagged almost instantly. You are living on the knifes edge on the first day, doing something a bot would do and there is no mercy from their system.
Posting many media files and pictures ends you shadowbanned fast too.
You basically have to gather karma points on smaller subreddits.
I think due to fingerprinting of hardware identifier (especially if you really use the app), they can tell if you upvote your own accounts, which leads to the banning of both of them - I would advise against excessive use of that method.
I think scammers are abusing karma begging/farming subreddits to give themselves karma points that way, it may be a method to accelerate it for yourself too.
I think Reddit app is a massive bloated spy app. I will not use their app on my smartphone. There are several alternative frontends that can be used without an account, even for accessing age-restricted content.
Every comment and post on Reddit is logged by third party entities nowadays, just within a few seconds. Assume everything you post there will be kept forever, even if you delete it. Your Reddit visibility setting has no effect on that.