Linear has been such a breath of fresh air, with such a solid desktop app (on Mac OS) that I don’t ever want to go back. Stuff happens instantly, the layout and semantics are an excellent “90% good enough” that I would happily relegate jira to only the most enterprise of enterprise projects.
There are lots of things where Jira falls short, but the pain points on an under-resourced self hosted instance of ten years ago are nothing like the ones you'll find on Jira cloud today.
It takes markdownish input but converts it to rich text as you type - so asterisk-space starts a bullet point list, etc.
I actually can't remember if it has a dedicated markdown mode anymore; the rich text editing supports the usual shortcuts that mean I tend to stick with it.