Oh it’s been a topic 
, at least in terms of SSDP and mDNS.
At present have the following options* if only using Mikrotik gear:
- Use bridge filtering, most current is here mDNS between VLANs with just bridge filters - Look Mum, no containers! - but only applicable to mDNS and SSDP
- Use a container with avanti/mDNSresponder/etc., but not all router have container
- Wait for Mikrotik, see mDNS repeater feature
MikroTik is working on mDNS repeater, but that will come together with a global DNS overhaul and it will be an improvement in all areas, not just this one. This is also why it takes some time to make.
- IGMP proxy or PIM-SM might work for some multicast discovery protocols… but does not work for mDNS, typically used by printers - so not really an option
- Some protocol use unicast DNS static hosts (or SRV records) or DHCP options as alternative to multicast discovery, but /ip/dns does not support PTR records so DNS-SD (the “normal” DNS version of mDNS) cannot be setup using Mikrotik DNS - so also not an option for printer or other mDNS things.