There was also Swarmpit but it didn’t really get that much love, sadly: https://github.com/swarmpit/swarmpit/issues/719
Portainer is pretty nice feature wise but even with lowered MTU I still get odd networking related issues (seems like the agent or whatever cannot reach the manager sometimes) but I’ve had those sorts of issues across multiple different clusters, both in cloud and on-prem with single leader setups and across both RPM and DEB only clusters. Weird stuff, otherwise perhaps the most established solution for Docker Swarm.