Some background on why gliders (have to) use FLARM:
We have been using FLARM in gliding since ~2005, and it is mandatory at all contests/regattas and even mandatory in some countries or clubs. Almost every glider in Australia has had one for more than a decade now. It's very entrenched.
When gliders are soaring we are looking for thermals, and when one glider finds a thermal the surrounding gliders will want to use the same thermal rather than trying to find their own and risking outlanding.
This naturally brings gliders together very frequently, and it is quite common to fly an entire flight in close proximity (<1km) from your friends. This is practiced and trained for and generally a non-issue because they are highly manouverable with good visibility, but very occasionally pilots get it wrong.
A naive collision detection system would alert non-stop in a situation with so many aircraft in close proximity. FLARM has patented a number of algorithms such that their collision detection system understands the movement of gliders in thermals such that it will only alarm when the pilots have missed each other and are actually likely to collide.
So I'm afraid we can't just get rid of FLARMs and change to ADS-B, as it simply won't function to help prevent collisions between gliders, of which the risk of collision is much much higher than to any other aircraft.
As for the frequency/SkyEcho, FLARM uses the 'ISM' band (https://en.wikipedia.org/wiki/ISM_radio_band), which is a general-purpose unlicensed radio band allocated by the ITU, unfortunately the ITU allocated a different frequency range in AU/US to Europe.
uAvionix will have to explain whether it's a legal issue or a hardware issue as to why the SkyEcho can't receive the ISM band in Australia (915Mhz). If that could be solved it would be great.
There is hope though, more modern FLARM's can have ADS-B IN, and we then see power aircraft with ADS-B OUT on our instruments.
Some pilots especially in busy areas are now fitting SkyEcho's to their gliders using the grant scheme, but they are unlikely to have alarms or displays showing power aircraft due to space and excessive alarming (from other glider) concerns. Glider cockpits are small and we can't just add another iPad.
A very few ultra-modern gliders have certified transponders with ADS-B OUT - until recently the power consumption of transponders/ADS-B was too high for gliders running off battery power only. Transponders are generally prohibitively expensive to retrofit relative to the cost of most gliders, even with the rebate. Most gliders are only worth ~20,000$.
On glider radios:
Gliders by and large have the exact same radios as RAAUS aircraft, there's no reason for them to be any better or worse. Often gliders flying with their friends in Class G airspace (where gliders largely operate) will be listening on one of the allocated gliding frequencies, so you may not be able to reach them on the area frequency.
Glider pilots have to hold a radio operator licence same as all pilots, and have to have biannual flight reviews where this should be checked. Of course there are still bad apples who don't do the right thing, but it's not as though glider pilots are unlicensed cowboys talking into tin cans.