As the A400M is an Airbus aircraft then if ATSAW is embodied then it will detect and display ADS-B only traffic as long as SIL=1+ and SDA=1+.
Here is what the ATSAW symbology looks like:
The same goes for Voyager too - with ATSAW embodied and enabled then it could see a glider if it is emitting SIL=1+ and SDA=1+ ADS-B. This is what Airbus say about ATSAW for the A330:
Airborne Traffic Situational Awareness (ATSAW), took advantage of Automatic Dependent Surveillance- Broadcast (ADS-B) by displaying aircraft information. It enhances the flight crew’s knowledge of their surrounding air traffic situation, contributing to fuel savings by identifying the opportunity to climb and optimizing the flight level. In approach ATSAW increases runway throughput by improving identification and information of target aircraft and decreasing pilot workload. ATSAW was certified in 2011.
However, not many gliders even have a transponder.