Good method for remote user testing using your own participants?

I'm new to this community, we're looking for people who have been in the same situation as us and could maybe offer some tips.

We're an established company, with thousands of users; and we specifically want to use our own users for the usability testing (since they are already qualified users and have some knowledge of the product already), we're not interested in recruiting a group of random participants from a panel of testers.

Our app is a web app, behind a login. We have noticed a lot of usability testing tools are best for websites, such as eCommerce sites, hotel booking sites, etc, which are suitable for a broad range of users accessing a public website. Our app has a specific target audience and has a login to access the apps feature.

We also want to automate as much of the usability testing as possible, so our UX team doesn't have to be on the calls with them in real-time.

Ideally, we'd be able to generate some usability test link, which we can then send to our customers via the Intercom widget or through a newsletter inviting them to participate. The customer would then be able to record their screen and speak their thoughts aloud. Our UX team can then go into the tool and review all the videos.

The most important thing is to make the user experience on the participants' side simple - ideally, they should not spend a lot of time installing software and setting everything up.

How can we best gain user insights from our current userbase?