If the phone does not boot anymore or doesn’t even startup into fastboot mode or recovery mode you are out of luck.
Some time back one in this forum explained that there would be a low-level option fiddeling with electronic parts directly and read out data. But iirc it would only work if the data wasn’t encrypted. Anyway you first would have to find some individual capable to even do the magic with contacting chips on the electronic PCB.
My quick search here brought me to this. There are other ways which are not easier though.
I also read of the company CBL.