I used to do that with Sony A1/A74 and GM lens. but it's too bulky/heavy and sometimes i just leave it in the hotel room. The best camera is the one with you. End of the day, if you not printing huge prints or doing stuff like birding, and only upload to social media, not much difference in quality due to the compression. Sure, one may look better than the other but to 99% of your audience, the gear wouldn't matter much.That is true for your daily driver la. But for those special occasions, I think you can afford to lug around a heavier camera that actually takes better photos and videos than the best mobile camera platforms.
For video, don't forget still need to edit and stuff. Import to pc, edit, export, upload. phone can straight away upload. it's much more convenient.
Of course there are some shots only dslr/mirrorless can, but for majority of the stuff, phone is more than good enough
