Good news, you can replace the text in most areas of the app: this includes your Instagram Bio, in the comments you leave, in your Stories, and even in direct messages. Although you can change the font on hashtags, sometimes it makes them difficult to read.
One of the most used is probably Instagram Fonts. This page allows you to see how your text would look in different font styles, including bold and italic. It also allows you to create your own fonts and text symbols:
Another useful website is Cool Fancy Text Generator, which also lets you insert emojis, symbols, and icons. Also, if you click Decorate you'll gain even greater customization options.
For both sites, just write what you want in the text box and choose the style you like best.
There are also a few interesting mobile apps with various Instagram fonts. We recommend Stylish free and contains 120 types of text, 20 types of figures and 60 artistic styles:
Another useful app is Cool Fonts, which also has an elegant and professional interface. Of course, it is only available on iOS. Finally, you can also try FancyKey, which also includes a keyboard to search for GIFs, emoji keyboard, keyboard themes, and others.