Ok. Probably echo link then. In short - the repeater uses the internet as another transport. Other repeaters can link up, or you can even use their application to activate repeaters right from your computer.
You can also do similar things with other digital modes (DMR etc) but they require special radios that speak that standard.
Interesting - why avoid asterisk?
I looked into fusion to play with but I’ve been using asterisk casually since like the 00s with no issues.