Seems like a fair question. I would be interested too if someone works this out.
One workaround might be syncevolution --export ... and then use the resulting data in whatever way gets you the functionality you need i.e. in some other “database”. Whether that is reasonable depends on how dynamic your list of contacts is. If you imported 300 initially but now only add 0 or 1 or 2 new contacts a day, it might be OK.
(I used syncevolution --import ... via the Librem 5 “goodies” package to do my import initially. I haven’t tried --export though.)