You can get a Canon M mirrorless body, which has the advantage that you can get an EF to EF-M adapter that'll give you full use of the lenses you already have. Downside to that is that the future of M is a wee bit iffy, although compatibility with EF-S/EF-M lenses (with the adapter) mitigates that somewhat.
Other options include:
1. Sony, which also has the advantage that there's an upgrade path from an a6x00 series camera to full frame if you switch over to Sony entirely. And you can even get adapters to mount your Canon lenses on the Sony with... some compatibility. Depending on how much you pay for the adapter, ranging from "Not bad" to "Absolute shit, so you'll have to use it in manual focus mode". Also, I personally hate Sony's user interfaces and find their cameras super frustrating to use.
2. Fuji. Great user interface, great controls and ergonomics, but I don't think there are any decent EF-S to Fuji adapters as of yet, and Fuji glass is priiiiicy.
3. Go balls-out and drop $1300 on an EOS RP. Sell your lenses and get new ones, either EF or RF. All the advantages of the 80D and then some, plus it's smaller than your T3i, plus FULL FRAME, plus it's the most likely mount to survive the current mount shakeup that Canon's going through.