Yes. When you use the PayPal form integration on 123FormBuilder for your online donation form, make sure to tick the option Payment represents a donation, as well. This way, the payment will be recognized by PayPal as being a donation.
Create your form and add a Number field, which will represent the donation box, and set it as required, if needed.
In Payments → Calculations → Assign Values or Formulas to Fields set your Number field with the value 1.
Do not assign negative values to your fields. Negative values aren’t recognized by PayPal.
In Summary and Discounts multiply the Number field with 1. Now people will be able to donate from 1 dollar, euro or whatever the currency you have set up.
The recurrent payments option will not work with donation forms. The two options can not be enabled on the same form.