Yes, big BUT, One of the consistent features of mirrorless cameras across brands is a shorter sensor to flange distance -- the lens mount is closer to the sensor. Your DSLR had to mount the lenses further from the sensor in order to clear the mirror in the camera. This in fact required some lenses (wide angles) be compromised in their design. Given the opportunity all the mirrorless designers immediately shortened the lens mount to sensor distance. Therefore an adapter is necessary to mount your old lenses on the new cameras. If it exists (not real likely) an adapter that retains full function of features like auto focus and auto exposure is going to cost and may perform with some compromise as in auto-focus works but it's slower.

On the other hand a dumb and inexpensive adapter is likely available to mount nearly any old lens to a new mirrorless camera. The lens will then work in Manual and/or stopped down Aperture priority and you'll have to manually focus. An advantage of the EVF in mirrorless cameras is focus peaking and so manual focus is very precise.

I use a lot of older manual lenses on my mirrorless cameras and am very happy with the result. At the same time I'm not into sports/wildlife or action photography. I've enjoyed being able to use basically any lens on my mirrorless cameras. For macro-closeup photos I use an old enlarging lens which works really well.

The shortened flange distance has freed up the designers to give us some better lenses in the wide angle range. I use a wide angle (14mm) for my Fuji cameras that is distortion free -- something DSLR users simply can't have.