Samba 4.13.14-Ubuntu panics when a connected macOS client reboots

No, you will need to install from source. Best you can get from a PPA is 4.14 (the "samba latest PPA" was not updated for 178 week days).

PANIC (pid 1772): Signal 11: Segmentation fault in 4.13.14-Ubuntu

You might get a better result with a couple more lines above and below this error. This one line did not have me find someone else with the same issue.

Segmentation faults are security bugs and as such will be back-ported into all supported releases. There faults are pretty common for samba; I have seen them in every samba version and 4.15.2 is already not perfect either so installing from source might not fix your issue. So it might be better to file bugreport and wait for an update.

The issue was this line in my smb.conf...

server multi channel support = Yes

Apparently, this experimental feature doesn't work well prior to 4.15 (while I use macOS clients, probably happens for other types as well). Turning it off solves the issue.