Newsletter landing in promotions or spam (need help)

Further to what others have said, don't try and game the system by getting around categorisation in inboxes. Tools giving you previews of where emails will end up are only guesstimates.
Inboxes are personalised to the user as well as the general algorithmic setup, which is constantly changing, so there is no full proof way to stay out of a Promotions tab or any other categorisation.
Gmail has now also provided a way to highlight yourself in the Promotions Tab. Again, this isn't guaranteed to show to everyone, every time but its a way to stand out.

1. What do your subject lines and preheaders look like? Following best practices?
2. What does your email content look like? A lot of images or a balance of copy and imagery?
3. Have you looked into BIMI or another type of email client specific authentication practice? BIMI is fairly new but it's gaining traction and is a way to personalise how you look in the inbox. An example is an image coming up in the icon roundel in Gmail, before the from name and subject line.

Don't try to game the system or attempt to hack your way to your preferred placement. It could do the reverse of what you're hoping and be hugely detrimental, causing your IP and from address to be blacklisted.

Just do the basics right and always remember that although people have given you their email address, there is no guarantee they'll even open it or even use email that much!

A good resource in the email marketing industry for best practices are Litmus.com & Emailonacid.com.
Both are dedicated testing preview tools but are very vocal in the industry and are always releasing blog content around everything you can do to optimise your placement.

In addition to what others have said, there are some formatting, copy, and image considerations when it comes to getting out of Promotions and getting into Primary tab. Unfortunately, there isn't a clear answer on how to get by the algorithm, but the below article helped me with the things to consider:

https://keap.com/business-success-blog/marketing/email-marketing/how-to-keep-your-emails-out-of-the-gmail-promotions-tab

I've also used this tool and really liked it. You can send an email to test accounts and see where it ends up:

https://www.gmass.co/inbox

Had a similar problem with Unheard Roots, I solved it by asking people to move the emails to their primary folder and replying to my emails

Readers must "reply to". Even one percent will help you solve the problem. So use mild methods to get readers to "reply to".

Use a proper email service provider (like mailchimp, convertkit, mailerlite, substack, etc)

Make sure you domain has dkim set up. Most providers will give you instructions on how to do this.

Don’t try to manage in an email client like zoho / gmail. You’ll look like a spammer. And it’s very difficult to stay legal with allowing unsubscribes and keeping data secure.