This really depends upon your budget and how serious you are as far as wanting to go. I have a Nikon, which I do like, I've always had the debate of mirrorless or the standard dslr. Whenever I shoot landscape, I shoot in mirror lock up mode to reduce the "slap" and helps with a cleaner shot. But I bought my D810 on ebay a couple years ago about $1200 less than what they go for new. It only had 4K shutter actuations, so basically it wasn't being used (backup camera). I shoot a lot of low light scenes and have been happy with my camera. Great in between cameras that cross over as professional and are steals could be the Nikon D750 or the Sony A7III. Maybe check on the A6500 as well.
I don't know if that helps, but if you have any other questions, just PM me.