Install a FTB Unstable 1.20: Fabric server through the Control Panel (Servers → Select your server → Game servers → Add Game Server → FTB Unstable 1.20: Fabric)
ScalaCube has worked great for us. We rented the 6GB plan for a 250 mods modpack for 10 players aprox, and so far (15 days in), everything has been great.