TikTok does support RTMP live streams, although not all users can access it. If you do have access to it, look for Transfer to PC/Mac from the Live screen. Tap Start Live to generate a stream key and stream URL to add to Riverside.
Please note that live video on TikTok uses a 9:16 ('portrait') frame that may crop out some participants in the Riverside Studio.
TIP: Export Video for Social Media with Vertical and Square Aspect Ratios
Use Riverside's Editor to change the aspect ratio of recorded clips, including 9:16 or 1:1, to share them on social media. You can also arrange and trim the videos before exporting them.