I think if the TEI is to move away from mailing lists to something more modern (i.e. more transiently fashionable) such as Discord or whatever), that should be decision for the whole community to take.* But it doesn't make sense to mix random queries and discussions with tickets, partly because queries and discussions benefit the whole community, and everyone sees them when they show up on the mailing list. When someone raises a ticket, only a small subset of the community will even be aware of it.

*Personally I think mailing lists are excellent for our purposes, and it's no bad thing to encourage younger users to get familiar with them. But if we were to migrate to something else, I think it should be a complete migration, rather than fragmenting the community discussions across multiple platforms.