Do you organize events from time to time? Whether that event is in person or online, you can use sites such as Eventbrite to get the word out.
If your event is free to attend, then it is free to post on Eventbrite – just be sure to link to your website!
Try linking to a specific page (such as about the event) rather than the homepage. The goal here is to build some link equity (strength) on interior pages.
The added benefit of Eventbrite is that many people discover events from the app/website – you might gain attendees in addition to a link.
Do you have an event coming up that you can post on Eventbrite? Do you use another event planning platform? May as well post your event in Facebook Events while you are at it… gain more exposure